Once upon a time a bar owner near where I lived was making potato shooting guns out of pvc pipes etc. One of my friends had one. To use it all you had to do was unscrew the back and spray a little bit of hairspray in there. You then turned a little wheel and then, hopefully, it ignited and the potato came out the other end.

Of course being teenagers at the time we decided that potatos alone were not good enough. We figured out that 1/2 a potato, then some other payload, then the other 1/2 of the potato on top delivered interesting results. Dog food was an interesting payload, as were rotten apples fallen off the trees.
The BEST however, IMO, was when we found a pair of underwear, complete with uh ... "racing stripes."

We loaded those babies up and fired, aiming for a group of bushes in the nearby woods. Unfortuantely the wind had other ideas and they ended up right near the VERY top of a 100 ft tall Douglas Fir tree. Green and White (and some brown) being high contrast colors, they were soon spotted by my friend's parents. They weren't exactly thrilled and we spent the rest of the day trying to shoot them out of that tree. The payload of choice for this task was apple in the bottom, canned dog food, then rotten apple on top. I'm sure we hit it, but those underwear were in there for good. Soon we were out of rotten apples and hairspray so we just left them there. Fortunately the wind took care of the underwear and we properly disposed of them.
