Many a fine time was had by me and my friends when we finally decided to build a potato cannon. For those not in the know, the PC is a bunch of PVC stuck together in the shape of a cannon. You put the potato in one end and hairspray in the other, ignite it and BOOM: French Fries at 400ft.
Of course it takes a short while to get the hang of it, and we had our fair share of times were we nearly lost good men when the thing went off a full 10 seconds after clicking the igniter and we weren't expecting it. There was also the time when the potato embarrassingly made it's way up the tube at a leisurely pace until it popped out the end to roll four feet.
Most of the time though it was WAY COOL. Firing it into the ocean or onto parkland at impressive distances and then doing a runner as nearby homeowners came out to inspect what the hell that noise was provided much enjoyment. Eventually we got smart, cut the thing in three and put threads on the ends so we could quickly pull it apart and put it back together again. We even tried building a silencer for it (didn't work for us). I'd recommend the whole thing to everyone other that the fact that its pretty dangerous; even with us being crazily careful with it we had way too many near "oh shit" moments. So kids, don't build one without mummy or daddy's permission!
I'm still half serious about having a 21 potato-gun salute at my funeral though...