O.K. very small guns. Homemade toy guns at that. Jeff over at Alphecca had a video of a fellow making a toothpick gun from a single clothespin. I have to admit I liked the shotgun-style slide action cocking and the economy of making the whole thing from a single pin.
Here's my version, somewhat more elaborate, which I used to make in grade school:
Modern clothespins with the open wound coils are noticeably weaker than the tight wound ones of days of yore. Evidence of the decline of western civilization.