Infinite Shotgun

There is a glitch in the last level of Halo 2, The Great Journey. Once you near the end of the level (when Sergeant Johnson blows open the Control Room), go inside and kill all of the Brutes and grab the Shotgun from one of the dead Brutes. Grab a couple of plasma grenades, otherwise this glitch will not work. Go into the room and watch the cutscene of Tartarus trying to get Miranda Keyes to activate the ring. Now, stick a plasma grenade to the Brute with a Shotgun. Make sure he drops his weapon and tries to charge before the grenade explodes. Now, reload your Shotgun and pick up the Shotgun rounds. It should give you enough rounds for a full Shotgun and you can come back to the Shotgun anytime to get more rounds. It has an infinite supply of Shotgun rounds.