if it is on the multipayer you need to have halo waypoint and a certain achievement. if not i dont know
He is wearing the Commando helmet that you unlock by ranking up.
Do a bulltrue in matchmaking to unlock the avatar award.
Commander
5h1t
It is actually called something else that I can't remember, but you unlock it in the E.V.A. helmet as an accessory after you buy every other helmet and accessory.
You have to play the levels in order. You can only select to play a certain level if you've already completed it in the campaign, either solo, or with a friend.
Unlock all 49 achievements
Simple: you must be rank commander or higher. Emiles helmet is a helmet of its own.
there are no cheats but you have to do tasks to be able to unlock them
Hax
to unlock the cat suit in tomb raider anniversary you need to find all relics in all the levels and then beat the entire game in tomb raider mode.
Inheritor, the last rank in the game. The last helmet, the Haunted Helmet, is the Pilot Helmet with a skull on it. To unlock it, you must reach the rank Inheritor, and own every BASE helmet in the game.