Using drainage pipe and masking tape for building the weapon, and hairspray as a propellant, the Kartoffelkanone can shoot a potato 200 meters and is able to split a person's head at distances less than 15 meters, or penatrate a wooden wall at 90 meters. The German government is moving to outlaw them, and some websites such as Kartoffelkanone.de have been removed from the web. Sites like http://www.kartoffelkanone.net/ are still up, however, and there are online forums and websites (mechanically translated from German) where people talk about how best to make the ultimate spud gun. There are also sites in English now...
Sounds to me like the
