Lego Crossbow

One day I was making a simple little elastic gun to shoot Lego blocks and I thought to myself, "it would be cooler if it had some kind of trigger." The next thing I knew, I was involved in a competition with my own self - I tried to imagine the most impossible thing to make Lego do, and then set out to figure out a way to do it. About 300 hours later (in hindsight I probably should have spent the time canvassing for UNICEF or something more noble) I had a semi-automatic pump-action lego crossbow that took four blocks in the handle and one in the chamber. It can fire a standard lego brick about 20 yards. It's not terribly accurate, but believe me, you don't want to fire this thing at the family pet.

This view shows the front of the bow with arms extended, one brick in the chamber, and ready for firing.