Okay the 4th of July is approaching fast. Here is a nice little cannon that launches potatoes at a considerable velocity. Using simple tools and common materials, you too can enter the world of backyard ballistics. The potato cannon uses either pneumatic compression or a combustible aerosol such as hairspring to propel the veggies down the PVC pipe. ;) Just be careful or you will shoot your eye out. These are NOT toys!!! One smartass kid was putting frogs down the barrel and launching them till the gun jammed. Einstein put his face over the barrel to see what was up and the frog fired, fracturing his face and blinding him for life in both eyes. Not kewl!!!
Check it out here - This website also sells kits if you don't have the skillz to do it yourself.