Swiss mini gun
The Swiss Mini Gun, produced in Switzerland by SwissMiniGun, is considered the world's smallest working revolver. The revolver measures merely 5.5 cm long, 3.5 cm tall and 1 cm wide, weighing only 19.8g. Ammunition is 2.34mm rimfire, also produced by SwissMiniGun. There is a key ring holster that comes with the gun when it is bought and can be clipped to a belt loop. Many countries, including the US and the UK, forbid the importation of the Swiss Mini Gun due to the ease of concealing the revolver.
Swiss Mini Gun is recognized by Guinness World Records as the world's smallest working revolver. It is a double-action revolver and has all the same features as are found on a real size gun. The manufacturer's website claims that "the manufacture of this exceptionally miniature revolver has only been made possible by exploiting the expertise and technologies of the Swiss Watch and Jewellery Industry."