Fighting doesn't really require any projectiles at all. Young people should consider dance-fighting or rap battling. I can remember "ranking" on people back in the day. I even bought a book of 101 insults to hone my skills. Maybe reading is the answer in another way: book battles! Do drive-by readings of Ogden Nash poems (they're short). Or form argumentative book clubs. Books are even free at a place called the library. Tupac read books, and he would have benefited greatly had his rivals called him out on his interpretation of the ducks in Catcher in the Rye rather than gunning him down.
Racing is also a good way to settle differences, but not with loud and dangerous cars. Running or even speed walking would do the trick. Or get some turtles from a local pond, and have them do the racing for you (just don't hurt the turtles). If you're not fast but are muscular from time working out in the prison yard, then have a pose-off. Or if fashion is more your thing, then a fashion battle.
The point is that there are all kinds of ways to compete if you don't want to kill one another. Paintballin is obviously not the best solution to avoid killing one another. Oh, and remember this?