King of the Hill (game)
King of the Hill (also known as "King of the Mountain" or "King of the Castle"), is a children's game, the object of which is to stay on top of a large hill or pile (or any other designated area) as the "King of the Hill". Other players attempt to knock the current King off the pile and take their place, thus becoming the new King of the Hill.
The way the "king" can be removed from the hill depends largely on the rules determined by the players before the game starts. Ordinarily pushing is the most common way of removing the king from the hill, but there are significantly rougher variations where punching or kicking is allowed. As such, the game is often banned from schools.
Use as a metaphor 
The name of the game has become a common metaphor for any sort of competitive zero-sum game or social activity in which a single winner is chosen from among multiple competitors, and a hierarchy is devised by the heights the competitors achieve on the hill (what Howard Bloom called "the pecking order" in his The Lucifer Principle), and where winning can only be achieved at the cost of displacing the previous winner. The game also lent its name to King of the Hill, an American animated series.
In video gaming 
The concept of "King of the Hill" in video gaming was introduced by Core War players who would pit their warriors against each other's in fit for survival. King of the Hill tournaments have existed for Core War since the 1980s.
King of the Hill has been featured as a game variant in many video games, especially first-person shooters like Halo: Combat Evolved and the more traditional Perfect Dark and more recently Gears of War 2. It's also an option in some top-down games, such as many of those in the Army Men series. In these versions of the game, a player or team of players must keep control of a specific area or object for a predetermined amount of time. When that amount of time is reached, the round either ends or a new area is designated on the map. In the virtual variant, players are generally removed from the hill by killing them.
King of the Hill is also a popular game on Internet forums in which the posters take the hill from the previous poster, only for it (usually) to be taken away by the next, and so on.