Most people know potato guns are sweet as hell. Unfortunately, if you want to use one to turn any large pieces of produce into a smoothie (a squash or watermelon, for instance), you’ll need something stronger than a potato. Say, a steel-reinforced potato.
With a trip to the drug store, the grocery store, and the hardware store, you can make a cannon that shoots potatoes over a hundred yards. All you need to do is know a little about gas laws. And promise you won't use this for evil.
There's nothing quite like the home creation of deadly weapons. I mean, what could go wrong? This beautiful $11 wall chart explains how everyday materials can become a propane-powered flamethrower, and there's a potato cannon version, too. Take a look: