Is there anything more fun in the DIY world than gigantic cannons made from PVC piping? I say no. Proving my theory is this pneumatic cannon, built from the aforementioned pipes and hooked up to an air compressor. It launches everything from potatoes and pumpkins to sprinkler flags and brooms, all while emitting a low, creepy moan with every shot. I'd say if you build one yourself to be safe, but I always say that. This time, I say mix it up: don't be safe. [Make]