Well I have had a potato cannon for a long time now, but I have been using tennis balls because they have a better seal in the chamber which gives the shot alot more power and range. Now I got bored today and looked up "Tennis Ball Cannon" and stumbled apon this little toy.

http://www.beercheckers.com/tennisballgun/cannon.jpg

But don’t spend $75 at this web site and buy it all made and ready to use, nooooo spend $50 or less at your own local hardware store. Here is the web site on what to look for to build this fun little gun.

http://www.kinkopf.com/tennisballgun/

Well once you get this cannon all set up you can be the first one on your block to kill a small child with a tennis ball...MWAHAHAHAH! O and i seem to find that "Aqua Net" hair spray works ok but i think that "Ronsonol" lighter fuel works really well, you can even try mixing them for a Big Boom!