In what consist this game glitches?

After you start a new game, you can exit back to the main menu, open multi-player, select death match, turn on infinite weapons, start the match, back out of it, go back to single player, and push start to resume your game. (Doesn't work if you hit x) You will then have infinite weapons. Only works on the unpatched version of the game.

Your save must have either beat or lost the first level. Faster to beat it however.