Swear. Some of the dudes would coat their paintballs with extra plastic so it wouldnt break no matter how hard you get hit in the face >:
I've heard stories of some idiots that would put their paintballs in the freezer until just before going out, making them as hard as rocks.
I know someone who plays paintball.. He's actually done this..
I'm not really into it, I had a gun, but I never actually played paintball, I'd just shoot ***around my house.. But if I found out someone was doing this, I'd beat them with the butt of their own gun, or the Co2 tank.