More:Halo 2: Missions: Armory

From GameWinners

Contents 1 Easy completion 2 Skull 3 Hidden areas 4 Funny dialog

Easy completion

When playing under the legendary difficulty setting, get to the part where you are in the shuttle bay where the Covenant have boarding craft attached. You can complete this level in two ways. The first is to kill the Grunts with the battle rifle, then pick up a plasma pistol. Use the plasma pistol to lower the Elite's shields, then quickly take out the battle rifle and kill them before they take cover. The other method is to get a number of plasma grenades and stick them on Grunts. They will run to the Elites and kill them.
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Skull

 Xbox  Under the legendary difficulty setting, complete the orders until someone asks you to go in the elevator. Wait until he says "Will you come in if I say please?" and walk in. When you get into the tram, face the Earth and hug the wall. Hold X for the entire ride. Eventually you will pick up a skull that says no clue to what it does (no word will appear, as with the other hidden skulls). Note: You cannot keep it as a weapon, as it is taken away after the intermission sequence. However, you can beat up the man with it. This skull appears to make enemies more aware of your location.
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Hidden areas

On any difficulty setting, get to the air lock room with the two jet troop Elites. Shoot The first two Elites. Once outside, shoot the third. Then, go toward the gray shuttle docked just outside the air lock chamber. Jump on it and it will allow you to go to hidden areas.

Funny dialog

Start the mission. After the Marine says "Stand by, I'm gonna offline the Inhibitors", start jumping around repeatedly. Note: It is best if you jump over the table to your right when the Marine offlines the Inhibitors. The Marine will say "Hey, take it easy!" When you continue jumping around, he will say "Careful, you'll pull a tendon doing that", and when you still continue, he will say "Fine, but don't come crying to me when you rip your leg out of its socket."