The loading mechanism of the spud guns I had as a kid were ingeneous. The nozzle at the business end of the gun's barrel was poked into the tuber to load a plug o' spud the size of a Tic Tac.

Compressed air would propel this plug into the ear of one's victim, or, if the attacker was more than a pace away from said victim, the plug would merely slam into the victim's cheek or eyebrow.

Alternative ammunition:

Or so I was told by someone who was there.