The small toy gun that would fire pellets of potato at high velocity. You had to push the barrel of the gun into a potato and gouge out a tight fitting pellet then squeeze the handle as hard as you could to pop the potato out of the end. You couldn't do any damage with them and the ammunition was cheap - every parents answer to a request for an airgun.
In my research for this entry I found that spud guns in the USA are something completely different (and better) and involve firing whole potatoes from a homemade canon (you oughta see some of these things - they're crazy).
Do You Remember Spud Guns?
Do You Remember Spud Guns?