Here's two links that I'm willing to experiment with away from the eyes of my children. Any takers?
Office Supply Crossbow - anything that can do that to a soda can is just too cool not to try at least once.
Fly Airplane - this is, by far, the best idea I've ever seen - even better than making speakers from Altoids tins. What's more, you could leave some raw meat out, collect many, many flies, and make an entire squadron. Then you could shoot them out of the air with your crossbow.
God I need to get some sleep.