Paintball this Saturday. I haven't played it for a few years now, but I still remember how much fun I had the last time I battled.
I had an incredibly sore back afterward though. Crouching in real life is a lot harder than pressing a key on the keyboard. And getting shot at is somewhat more punishing that watching your health meter diminish on the screen.
Yeah I don't make combustion cannnons for those reasons. I make pneumatic ones. So far I have a ball valve one (max I've shot at is 130 psi) and am making a diaphragm cannon now. Paintball I reckon cost to much, you can make the same power pneumatic cannonns for $50 if your good at pvc construction.
Pneumatic potato cannons used air pressure to lauch potatoes and are stronger, safer and more reliable than combustion cannons which use hairspray (or another combustible spray) ignited with a bbq igniter to propel potatoes. On the other hand, combustion cannons are faster to set up and use than pneumatic cannons and are far less complicated to build. Some people also say that you can shoot many times in a row with a pneumatic and have to wait a little while between shots with combustion cannons because the chamber heats up, although if you do build a pneumatic DO wait in between shots for a minute or so because the rapid decompression in the chamber of the pneumatic cannons cools down the chamber very fast, making it so cold it may shatter if fired to much.
AND FOR THE LOVE OF GOD, NEVER EVER EVER LOOK DOWN THE BARREL OF HOMEMADE WEAPONS!
People have built hybrid cannons between combustion cannons and pneumatic ones that break the speed of sound 
. They do this by compresing air then injecting fuel, so lets say 1:10 for fuel:air ratio, the would put in 4 times the amount of air, allowing for four times the amount of fuel.
It didn't do it automatically. I put the link in because that's going to be the field we're playing in. Looks pretty cool.
I like laser because it is cheaper and in paintball the mask I got made it too hot (here in Australia today it was 38 degrees celcius where I live) and my gun jammed and the guns didnt have scopes unlike laser. Plus the laser battlefield are usually way bigger and cooler. Go to http://www.laserskirmish.com/ to check your closest place. Using the Morita sniper + scope to shoot people hundreds of feet away is fun " SRC="images/smiles/icon_smile.gif">.
EDIT: By the way, I checked out that paintball link. Paintball is much cheaper in America (and yes I did convert the currencies) than my area's one.
