Halo 3 cheats page 15

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More:Halo 3: Halo

Brute choppers

You must be on Legendary and playing in co-op mode or the choppers will not be there. After you come through the valley with the Warthog, just before you leave the snow turn left instead of going on the metal squares. Just past the rocks a short distance are two Brute choppers. You can now complete the level in style.
turin_illfate
Hidden Mongoose

When you get into your Warthog, go forward down the path. When you are supposed to take a right to the platforms, take a left instead. Follow the path until you are on some platforms. Look to your left. There should be a Mongoose ready for your use.
rdas Phil Wyatt
Dancing man in boxers

You need two players for this trick. Start the Halo level and keep following the path until you get to the part where you see a metal floor. Take a right up the icy path. Cortana should ask "Where are you going?" You should then see a bridge-like object. Go into the room. If you take a left there is a terminal for "Marathon Man" achievement. If you go to the right you will see a ledge in the distance if you do not turn on your light (D-pad Up). Have a player with a rocket launcher stand behind the other player. Have the player without the rocket launcher run up to the gap. The player with the rocket launcher must shoot when he is about to jump off. If timed correctly, the running player you should fly to the ledge. This may require a few attempts. Once you are on the ledge, jump to your left. Do not fall or you will have to start all over again. Walk forward a distance and you should see someone dancing in his boxers with no shirt.
Troy
Funny dialogue

On the final part of the level Halo, kist before you jump into the ship you will see a rock. Get out of the Warthog there and walk around the base of the rock. On a ledge is a lone Grunt screaming funny lines. He will not kill you if you get close to him. Note: You will end up trapped while talking to the Grunt, and must restart from your last check point.