Build a Steel Shotgun Pneumatic Cannon
You can have some dangerous fun with some pipe supplies from your local home store. This Steel Shotgun Pneumatic Cannon is a good example of that. For more items like this have a look here. "The Steel Pneumatic shotgun is a very simple metal spud cannon, so see how to make it in this video. It is specially designed for C-cell batteries, but will work with any projectile (granted