Hidden Weapons
Get on the mission Regret of Halo 2, it is best done on the Easy difficulty. Get to the part where you fight the two Hunters. Walk towards the Gondola, but stop right in front of it, don't walk on, now walk to your right, until you get to the ledge. Now look down off the right ledge. You should see a platform connecting to the giant platform you fought the Hunters on. The wall right beside the platform will hold weapons, stuck half way through the wall, though you can still pick them up. However, it's good to keep in mind that after you reach the hidden cache, you can't get back up to where you'd been, and also the weapons sometimes just won't spawn.