Some fictional sources describe the projectile as moving at significant fractions of the speed of light, implying an unrealistically high amount of energy given current human capabilities. The coordinate mass (mass accounting for effects of special relativity based on velocity) of a projectile is , where c is the speed of light and m is the mass at low velocities, where the effects of special relativity are insignificant. The kinetic energy of the projectile would be represented by , where m is the coordinate mass, and v is the velocity. As the velocity of the projectile increases, the total mass increases quickly, making it immensely hard for velocities of such magnitude to be attained. To date only microscopic particles have been induced to go so fast through human technology.
In fiction they can depicted as firing inert projectiles from orbit directly at planetary surface targets (EG: Babylon 5, series 2 – the Centauri invade the Narn home world after an attack using "Mass Drivers") as if the target and the shooter are not moving relative to each other, and do not have a gravity well nearby to effect the projectiles' trajectory. They point the gun at the target, and shoot, and hit the target, from orbit. In reality, at least if the muzzle velocity is not much greater than the orbital velocity[original research?], they would not be aiming at the surface, but firing behind their orbit, so that the projectiles would lose their orbital velocity and free-fall to the surface.
In the 1955 novel Earthlight by Arthur C. Clarke, an electromagnetically propelled piece of molten metal is fired from a fortress at an advanced warship, astounding a nearby observer who sees a beam of light (on the airless Moon) stabbing the warship and destroying it. Later it was shown that molten metal cannot be accelerated by a magnetic field as metal loses its magnetic properties in a molten state, and Clarke admitted his error gracefully.
In Harry Harrison's book The Stainless Steel Rat's Revenge gauss rifles are the standard armament of Cliaand soldiers.
The first mass driver known in print was called the "electric gun", a method of launching vehicles into outer space from the Earth's surface, in the 1897 science fiction novel A Trip to Venus by John Munro, published by Jarrold & Sons, London. Munro describes multiple coils fired in timed sequence by solenoids to achieve acceleration without excessive G-forces that would be harmful to the passengers. He also describes combinations of propulsion methods used in tandem, including electric gun launch of a vehicle with onboard rockets, compressed gas jets and even retrofired bullets as a means to increase velocity and change direction. He also discusses the use of aerobraking and parachutes for landing on a planet.
In the novel The Two Faces of Tomorrow by James P. Hogan, a Maskelyne mass driver based in the Sea of Tranquility is used by the TITAN supercomputer to easily destroy a lunar ridge to clear land for the construction of a second mass driver site.
In the novel Warrior's Blood by Richard S. McEnroe, an ancient alien mining colony is awakened from stasis and uses a mining transport mass driver as a weapon of mass destruction against the Earth.
In the novel Pushing Ice by Alastair Reynolds, the crew of the Rockhopper use mass drivers to send comets back to earth for processing into water and other resources.
In the novel series Buck Rogers, the protagonist uses railguns on the planet Luna.
In Redemption Ark by Alastair Reynolds, various factions use railguns, ranging from small ship-to-ship devices to thousand-kilometre installations, which fire explosive foam-phase hydrogen and other munitions.
In Count Zero by William Gibson, the characters speculate that a huge explosion was triggered by a railgun, and they describe the railgun's inherent instability: "You can rig a railgun to blow itself to plasma when it discharges."
In the Black Cat anime/manga series, the protagonist Train Heartnet is capable of shooting his revolver as a railgun, powered by electricity generated by nanobots in his bloodstream.
In the StarFist series, railguns are used by the alien Skinks against human soldiers.
In the Succession series by Scott Westerfeld, railguns are fired from the orbiting Lynx to kill the Rix commandos.
In Extras, the fourth novel in the "Uglies" series by Scott Westerfeld, the main character and a group of friends find a mass driver hidden inside of a mountain, built for the purpose of launching metal into orbit to be used in creating infrastructure for the human colonization of other planets.
In Old Man's War by John Scalzi, the CDF ships are equipped with railguns and various other weapons.
In the Legacy of the Aldenata series of books by John Ringo, the alien Posleen are equipped with man-portable rail guns in 1-mm and 3-mm versions, in contrast to the gravity guns supplied to the human soldiers. The Posleen also use launchers that are capable of accelerating missiles to a certain fraction of the speed of light (hyper-velocity missile launcher).
In the novel and anime/manga series Toaru Majutsu no Index and its spin-off Toaru Kagaku no Railgun, Mikoto Misaka can manipulate electricity with her hands to fire arcade tokens as projectiles, similar to a rail gun.
In Neal Asher's Polity stories, railguns are among the weapons used by Earth Central Security. In the short story, "Alien Archaeology", the main character mentions that ships hiding with chameleonware near ECS warships might find themselves the victims of a mishap involving a railgun test fire.
In the 1992 novel "Flare" by Roger Zelazny and Thomas Thurston Thomas, a mass driver located inside Mount Whitney in the US is used to launch small payloads into near-earth orbit. The facility suffers major damage during a solar flare when the operator ignores warnings and distortions in the earth's magnetic field cause a payload capsule to hit the exit gate. The driver is described as 11km long and using capacitor banks to deliver a two-second pulse of 18MWh of energy.
in Dana Stabenow's 1990 novel Second Star, a mass driver located at a lunar base is used to launch construction materials and other cargo to the first space habitat, in tandem with a mass catxher. The use of both are involved in leading to a key plot turn.
In the animeMacross, the SDF-1 has four heavy rail guns on its "shoulders" when it is in "humanoid" attack mode. It carries on board the Monster Mark II Destroids, each of which have four heavy rail guns with muzzle velocities of 4000 km/s in space, a speed that would make an explosive warhead redundant.
In animeGundam series such as Mobile Suit Gundam SEED, railguns of various sizes are mounted on both space warships and smaller one-man machines called mobile suits and mobile armors. The projectile does not have the speed and destructive properties of railguns depicted in other media. Mass drivers are also commonly used as a method of assisting the launch of shuttles from Earth.
In the animeRahXephon, the Vermillion is equipped with a combination weapon containing a continuous fire railgun and a beam weapon.
In the television series Stargate Atlantis, a railgun prototype is used against the Wraith Darts. It has a magazine size of 10,000 rounds and hits its target with a velocity of Mach 5 at a distance of 250 miles. These railguns are used as anti-aircraft point defense weapons, and are mounted on wheeled chassis like field guns. Various Earth space warships in the Stargate franchise are depicted to be armed with similar weapons.
In an episode of Dirty Pair, an mass driver is used to select numbers for a gambling game by launching asteroids at an uninhabited planet. After the game is found to be rigged, one of the victims of the scam damages the controls to the mass driver, causing it to fire on an inhabited planet.
In the role-playing game Tal'Vorn, railguns and mass drivers are relics of a lost technology and are still used by the Northar race.
In the post-apocalyptic role-playing game Rifts, the Glitter Boy character class is an individual who pilots a large armoured suit equipped with a railgun. The suit has a mechanism whereby it anchors itself into the ground when firing so as to avoid being knocked backwards by the gun's powerful recoil. Other Rifts character classes, specifically robots and cyborgs, have access to railguns.
In the world of Warhammer 40,000, the Tau railgun is one of the most powerful guns in the game available as a personal weapon. The Manta Missile Destroyer and Tigershark aircraft employ these in a long barreled version, and the Tau Hammerhead gunship has two different variants. XV-88 Broadside Battlesuits carry high-power twin-linked shoulder railguns. The Necrons also use several forms of Gauss weaponry, however this is a misnomer, as their weapons break inter-molecular bonds, and have no projectile.
In the BattleTech and MechWarrior series of tabletop, roleplaying and video games, many of the BattleMechs are equipped with "Gauss rifle" weapons. Various tanks, drop ships, and warships are also equipped with Gauss rifles, including a variant scaled up to act as a warship's primary weapon.
In the Infinity tabletop wargame, several of the Tactical Armored Gears are armed with Hyper-Rapid Magnetic Cannon or HMC. This weapon fires 3 mm tungsten darts at extremely high speed and with a fast rate of fire, capable of easily piercing even the toughest armor.
In the miniature game AT-43 the Red Blok, one of the games factions makes extensive use of "Gauss" Weaponry, ranging from "Gauss" Submachineguns to the mighty Heavy "Gauss" Cannon. However despite the reference to coilguns, the description of their operation indicates that they are railguns.
In the classic role-playing game Space Master, railguns are a common projectile weapon in 10th-millennium combat. In the context of the game world, they are called Magnetic Linear Accelerators, abbreviated as MLAs.
In the anime Dragonar, the Giganos Empire uses a giant mass driver on the moon to attack Earth although it was originally used for transporting large rocks. Before dying, the Giganos leader, Giltorre, orders Meio Platt to destroy it.
In the Starfire series add-on Alkelda Dawn, the interstellar race known as the "Umbra of Vestrii" use kinetic weapons.
In the Miniatures games Urban War and Metropolis, as well as their predecessor Void 1.1 the standard weapon for the more technologically advanced races is the "Gauss Rifle" and is accompanied by larger and smaller versions like Sniper Rifles and Pistols.
Some computer games feature railguns as weapons. The most popular type of ammunition for these railguns are depleted uranium slugs. A common trait shared by many railguns in different games is the ability for a slug (or other ammo type) to hit and pass though multiple enemies with one shot as well as allowing one to see, one shot kill, and/or shoot though solid matter by use of some type of x-ray or even a thermal aiming device (mainly in first-person shooters). This is conspicuously similar to the behavior of the railguns in the aforementioned movie "Eraser", which was released during the first person shooter boom.
Other traits can include these weapons being able to do electricity- or EMP-based damage because most railguns in video games use electromagnets as a main power source.
Ace Combat 04: Shattered Skies: The "Stonehenge" superweapon is a battery of railguns designed to shoot down asteroids, but effective against aircraft as well.
Ace Combat 5: The Unsung War: The Mass Driver at the Basset Space Center is used to supply Osean space units, and in mission 6, uses an SSTO craft to deliver a laser to the "Arkbird" spaceplane.
Ace Combat 6: Fires of Liberation: The "Chandelier" superweapon is an immense railgun mounted on a mobile, ocean-going platform that fires giant warheads containing cruise missiles (similar to MIRV missiles) at the Emmerian capital city, Gracemeria. The Estovakians' superfighter, the CFA-44 Nosferatu, is also armed with a pair of aircraft-mountable railguns, officially referred to as "Electromagnetic Launchers."
Alien Legacy: The mass driver is a planetary facility used for transporting ore from one mass driver to another remote mass driver.
Aliens vs Predator 2: human players have access to a scoped railgun used as a sniper rifle with a very loud report. In addition, the lack of muzzle flash on Predator spearguns and that they allegedly fire spears at relativistic speeds (impossible to conventional projectile weapons) point towards them being railguns as well.
Armored Core games: "Linear Rifles" and "Linear Cannons" are part of an ACs inventory of equippable weapons. They fire high-powered rounds at speeds high enough to visibly distort the air around them.
Battlefield 2142 (computer game): The Rorsch Mk-S8 is a stationary anti-vehicle railgun.
Battlefield 4: The Rorsch Mk-1 is a man-portable railgun rifle in the Final Stand expansion.
Battlezone II: Combat Commander: certain Scion craft can be equipped with Gauss Cannons; in addition, both the game and its predecessor contains a weapon named MAG Cannon (Magnetic Acceleration Gun) whose power depends on the amount of ammo used up before firing.
Crysis and Crysis 2: one of the weapons in the game is a bolt action Gauss Rifle, which can kill any human in a single shot and an alien with two or three well placed shots. The weapon emits a purple cloud when fired.
Command & Conquer: Renegade: When playing as Brotherhood of Nod forces in multiplayer mode, selecting the character General Raveshaw will enable the player to use a rail gun as an extremely lethal weapon regardless of where on the body the projectile from it eventually lands.
Command & Conquer: Tiberian series: The units "Ghost Stalker" and Mammoth Walker Mark II are equipped with rail guns. These devices sport the same bullet trail (tightly spiraling smoke in a straight line between shooter and target) as those in the film Eraser. Such a visual effect, however, is not representative of actual railgun operation. Cutscenes showing the Mammoth MkII in combat show the railgun shots instead as plasma-like energy with no visible bullet trail. In Command & Conquer 3: Tiberium Wars as well as in Command & Conquer 3: Kane's Wrath show GDI Zone Troopers and GDI Commando armed with portable rail guns, although the Commando's rail guns play a decidedly anti-infantry role. The GDI Predator tanks, Mammoth Mk-III, Guardian Cannons, Battle Base, and Titans can be upgraded with Railguns.
Dark Reign: The Future of War (game): Several Freedom Guard units and buildings use railguns, including Mercenaries, Triple Rail Hover Tanks and Railgun Platforms.
Descent 3: In this game the railgun is used primarily as a long distance attack weapon that leaves a momentary white trail.
Deus Ex: Invisible War: A weapon called the Mag Rail can fire a powerful energy beam which can kill most human targets with a few shots. An alternative weapon is an electromagnetic pulse which can be fired through walls and other obstacles, and which does heavy damage to all non-shielded electronic components.
Eve Online (a space-based MMORPG from the Icelandic software house CCP Games): Railguns are a popular turret weapon fitted to a variety of ships particularly favoured by the Gallente race. The main advantage of railguns in Eve Online is their extreme range of up to 250 km. The ammunition for these weapons are titanium containers filled with different elements (e.g. iridium) for different battle situations.
Escape Velocity Nova (a space role-playing game developed by Ambrosia Software): The Auroran Empire makes heavy use of railguns as ship-mounted weaponry. The railguns are offered in 100-(appearing primarily as a turret found on the AE Carrier), 150-, and 200-mm varieties, and are the farthest-shooting projectile weapons in the game.
Fallout: there are several Gauss weapons in the series. Fallout 2 features the PPK12 Gauss Pistol and the M72 Gauss Rifle, both said to be of German design. Fallout Tactics additionally features the MEC Gauss Minigun, of Chinese design, while Fallout 3 features another Gauss Rifle with a scope. Fallout: New Vegas also features a Gauss Rifle that is similar, but less efficient than the one in Fallout 3 as well as the unique YCS/186 Gauss Rifle.
Final Fantasy VIII (game): A coilgun is used at Lunar Gate on the Esthar continent to launch pods containing individual persons into space.
GoldenEye: Rogue Agent (game): The Mag-Rail is a rail-handgun that fires a depleted uranium spike roughly the size of a tent peg. Though capable of passing through multiple enemies, walls, and objects, they are unable to pass through vehicles and energy shields. Two can be wielded at the same time, and the weapon causes roughly the same amount of damage as the Harpoon RL's rockets. When fired, the barrels open as a new spike is loaded and then close, venting what is possibly a coolant gas through the gill-shaped holes behind the barrel.
Halo, Halo 2, Halo 3, Halo 3:ODST, Halo: Reach, Halo 4, and Halo Wars: The beginning level of Halo 2, Cairo Station, takes place on an orbital platform built around a large coilgun (a Super Magnetic Accelerator Cannon, or Super-MAC). The M12G1 Warthog LAAV has a back-mounted M68 Gauss Cannon, a scaled-down version of MAC technology. The human ships in the series are almost all armed with large axial MACs as well. In the penultimate level of Halo: Reach, a bus-sized mass driver coilgun is used to destroy hostile dropships and a battlecruiser until the player's allies, in the cruiser Pillar of Autumn, can be launched. Halo 4 introduces a hand-held single-shot railgun.
Heavy Gear: Railguns can be placed on the largest of the game's mechanized weaponry while even bigger railguns are used by tanks and landships.
Heavy Gear II: The New Earth Government (the antagonists in the game) use a large orbital mass driver to propel asteroids at planets.
Heli Attack 2 and Heli Attack 3 (games): Railguns fire a green beam of light, which can go through walls. In Heli Attack 3 there is also a railgun called the Anytime that shoots explosive projectiles.
Homeworld: Many ships in the game utilize mass driver weaponry. Weapon designs range from smaller rotating mass drivers to larger turret-based ones. There are no ammunition limitations.
Hostile Spawn: There is a rail gun available that can shoot through multiple enemies. Collectible energy cells are used for ammunition.
Mass Effect, Mass Effect 2, and Mass Effect 3 - the majority of weapons from pistols to 800-m spinal guns of dreadnought starships combine magnetic accelerators with the titular mass effect technology. Within the game, the fictional Element Zero can be used to increase or decrease the mass of the slug via dark energy, allowing to accelerate it to phenomenal (usually relativistic) speeds with little recoil, hence "mass accelerator weaponry". The projectile used is at the size of a grain of sand (in case of firearms), and is sheared off a large piece of metal - which lasts for thousands of shots - by the internal systems, ensuring that ammunition capacity is rarely an issue in the game. However, the thermal energy produced by the weaponry is enormous, managed by passive cooling in the first game and by ejecting single-use "thermal clips" in the second. The rail-gun nature of this weapon is confirmed by the upgrade options "Extended Rails" and "SCRAM Rails".
Similar weapons have been in use by the Reapers and the species they exterminated for at least 37 million years. One such weapon left a mark at the size of Valles Marineris by a glancing blow on a planet, located in a star system hundreds of light-years away from the intended target. An NPC can be heard warning a few recruits about the unlimited range of space-borne mass accelerators and inevitable collateral damage: "...you are ruining someone's day - somewhere, sometime!"
The series' Reapers features a "magnetohydrodynamic" weapon that, like Arthur C. Clarke's weapon from Earthlight, uses molten metal suspended and ejected by an electromagnetic field, along with the mass effect technology to accelerate it at a fraction of the speed of light. This gives it the appearance of an energy weapon. Also like Arthur C. Clarke's Earthlight, it has the same fatal error; molten metal cannot be accelerated by a magnetic field, as metal loses its magnetic properties in a molten state.
Master of Orion, Master of Orion II: Battle at Antares, and Master of Orion III: Warships in this series can be equipped with mass drivers and gauss cannons, once the appropriate technologies have been researched. Their distinguishing feature is that the shots do not diminish in strength no matter how far across the battlefield they travel.
Metal Gear Solid: The main weapon on the massive bipedal walking battle tank, Metal Gear REX, is a railgun (although the way it is described it seems more like a coilgun in operation) mounted on the tank's right "arm." It is discovered that the rounds it fires are actually nuclear warheads.
Metal Gear Solid: Ghost Babel: Similar to Metal Gear REX above, experiments are performed on the larger Metal Gear GANDER in order to test if it can fire nuclear projectiles through rail guns, which it succeeds in doing. This potentially makes it more feasible than REX, owing both to itsTemplate:Which one increased size and the dependency on a devoted power station to fully function.
Metal Gear Solid 4: Guns of the Patriots: "Boss" enemy Crying Wolf uses a railgun as her main weapon. It becomes available to the player after she is defeated. Also, the previously mentioned railgun (from Metal Gear Solid) becomes a central plot point, after Liquid Ocelot steals it and attaches it to the ship Outer Haven.
Ogame: Gauss cannons are one of the planetary defenses that can be built. They're the second most powerful defense, surpassed only by the plasma turret.
Oni: The player can equip his/her character with a weapon called the Mercury Bow. The Mercury Bow is an advanced sniper rifle that uses railgun technology to propel a frozen mercury sliver. In addition to the trauma caused by impact, the player's enemies are purported to suffer from mercury poisoning afterwards.
Outpost 2 (a strategy game by Sierra): Eden's medium weapon is a railgun.
Parasite Eve II (videogame): Aya Brea, the main character, can use "Hypervelocity", a railgun as a secret weapon. It also appears as a secret SDI weapon used by the United States government to rescue the world from a global pandemic, but proves fruitless as the main character ends up stopping it herself.
Pawn Tactics: A gun known as the "Gauss Rifle" can be used as a primary weapon in the Lancer class. It is said to be capable of penetrating thick steel and does more than normal damage against heavily armored classes.
Perfect Dark (for Nintendo 64): One of the available weapons, the Farsight, is a railgun with an X-ray scope, allowing the player to shoot and see through walls. Also, in Perfect Dark Zero for Xbox 360), contains a sniper rifle called a Shockwave also has an X-ray scope that both allows the player to see and fire charged particles though walls.
Policenauts: Jonathan Ingram and his partner, Ed Brown, stow themselves away in a shuttle launched by a lunar mass driver to escape the Tokugawa plant on the Moon after finding incriminating information.
Project Snowblind: The antagonistic organization "The Republic" uses automated railguns to shoot down helicopters of the coalition where the player serves. The Republic develops a portable "Rail Cannon" that the player later acquires.
Quake II: A railgun (having the appearance of a small vacuum cleaner with red-tinted electronics on top) was included as a weapon in the game. It fires a Depleted Uranium slug with a silver smoke trail and a blue spiraling plume. This incarnation of the weapon most directly was modeled after the Railgun in the movie Eraser.
Quake III Arena: A nearly identical weapon. The spiraling blue plume was eliminated and the color of the smoke trail was customizable by the player. The spiraling plume was re-added as an option in a later release, also with customizable color via modifying 'console variables'.
Quake 4: The railgun has a more compact redesign and recolored to a dark red and comes equipped with a scope. It still takes uranium slugs as ammo but now shoots a momentary green line with a spiral around it which fades quickly. The weapon later gets a power boost, giving the weapon the strength to penetrate multiple enemies and render weaker enemies a small cloud of blood in one shot. The multiplayer mode allows for rough color customization via the game menu with a much finer customization with 'console variable' tweaks. Quake 4's Railgun also features a zoom scope to aid the player in long-range engagements. The Railgun is arguably the most powerful weapon (per shot) in the game - easily taking 100 hit points from an armored opponent.
Enemy Territory: Quake Wars: The Strogg Infiltrator has a railgun similar in design to the Quake II one, though both parts of the trail are colored orange.
The FPS Requiem: Avenging Angel features a very powerful rifle-sized railgun. Until well into the final mission, the player only finds ammo and an incomplete (thus useless) railgun.
Resident Evil 3: Nemesis: An experimental military railgun nicknamed the "Paracelsus Sword" is used to defeat the final boss.
In the RT4X game Sins of a Solar Empire, a Gauss cannon is used as an orbital defense platform and as an ability for the Kol class capital ship. The TEC super-weapon, the Novalith, is a massive orbital railgun firing a large nuclear warhead directly at enemy planets.
Shadow Warrior: The rail gun found in the game shoots pieces of metal at near light speed, propelled from a magnetic field. This weapon will penetrate multiple enemies, making it powerful and very useful in certain situations.
In Skulltag, a source port of Doom. The railgun is one of the most powerful weapons in the game in terms of raw stopping power, it is inspired by the Quake III Railgun.
Spy Hunter (game): The Interceptor has a railgun that the player can earn late in the game.
In the S.T.A.L.K.E.R. computer game series, the C-Consciousness developed a functional Gauss gun which is powered by an electric artifact called "Flash".
StarCraft: The Terran Marine can be armed with a "Gauss Rifle."
StarCraft II, the Diamondback assault tank has a weapon called the "Eviscerator Rail Gun."
Steel Battalion: VTs in the game can be equipped with railguns, which, although powerful, are extremely heavy.
Steel Sentinels: Gauss guns and railguns deal kinetic damage like normal guns, but use up energy when used.
Supreme Commander series: The UEF faction favors gauss cannons as the primary weapon on many of their vehicles.
System Shock: Rifle-sized 'Railguns' are available, but the projectiles travel very slowly, no faster than a thrown grenade.
Tachyon: The Fringe: Special weapon used on Bora fighter-class ships, capable of destroying most unshielded fighters. Due to the game's non-relativistic physics, railgun shots are faster than lasers.
TimeSplitters: Future Perfect: One of the game's weapons, the Mag-Charger, is a railgun that can shoot through walls with a special thermal scope for aiming. Its projectiles are charged via electro-magnetic pulse (from which the weapon's name comes from) and does more damage to mechanical enemies.
Tanki Online: The rail gun is a powerful weapon that takes a while to reload but does a massive amount of damage
Titanfall: The player can equip the "Plasma Railgun" as the primary weapon for a Titan.
Vendetta Online: Railguns are one of the weapons systems that can be equipped.
Void Hunters: Mounted on space ships, mass drivers are short range, rapid fire weapons; railguns are long range and have high projectile speed.
The Wing Commander series features fighters with mass drivers. Strength and energy efficiency is above average, but muzzle velocity and range are lower than many other fighter guns. No ammo limits.
Warframe: The Corpus Lanka sniper rifle obtained from clan tech research is a railgun, though the description points towards it functioning more like a coilgun.
Warzone 2100: During both late-campaign and late-skirmish games, the player can develop and employ a number of railguns, ranging from the early-stage Needler turret up to the immense Mass Driver Fortress. Each version is relatively expensive to produce compared to equivalently-sized ballistic or energy weapons, though they do deal more damage per shot than all but the strongest energy weapons. Each railgun technology takes a comparatively large amount of time to research and produce.
Xenogears: It was often used to launch missiles and other items into space, especially during the Zeboim era. This was perhaps one of the key facilities during the nuclear war that ended the Zeboim civilization 4000 years prior to Xenogears. Taura used it to spread nanoassemblers that would deactivate the Limiters of the human race and reverse the effects of the Gaetia Key.
Xenosaga: One of KOS-MOS's weapons is a railgun called the "Dragon's Tooth."
X-COM: Terror from the Deep: The titular organisation has access to three Gauss weapons, said to operate on the same principles as alien plasma weapons from the game's predecessor, but modified for underwater deployment using conventional power sources.
XCOM: Enemy Unknown: a top-level shotgun-equivalent weapon is the Alloy Cannon, which apparently is a Gauss gun and an off-shot of the aliens' standard plasma weaponry, developed to remove the extreme barrel wear that plagued attempts to develop projectiles made of highly dense alien alloys. The result is the most lethal close-range weapon in the game. XCOM: Enemy Within introduces a literal Railgun as a mid-game weapon for Mechanized Exoskeleton Cybersuit troopers; it is an offshoot of earlier laser weapons technology, and is developed alongside an aircraft laser cannon and a hand-held laser Gatling gun, and takes form of a huge rifle (which is just the size for a 3 m tall MEC) with prominent rails. A single shot from it deals more damage than a long burst of fire from the Minigun it replaces.