Spud gun

A typical factory-made toy die-cast spud gun. The cap attached to the muzzle converts it into a water pistol.

A spud gun or potato gun is a small toy gun used to fire a fragment of potato. To operate, one punctures the surface of a potato with the gun's hollow tip and pries out a small pellet which fits in the muzzle. Squeezing the grip causes a small build-up of air pressure inside the toy which propels the projectile. The devices are usually short-range and low-powered.