First, you have to buy the base E.V.A. helmet, which you unlock at Major. After that, you can purchase a special accesory for it, which is Emile's paint on his helmet. It costs 60,000 credits, though, so start saving up.
Simple: you must be rank commander or higher. Emiles helmet is a helmet of its own.
For EVA u hav to be a major but Emile's helmet with da skull on it u hav to be i think a colonel
It should be standard on the right security shoulder.
You have to be a general, and you can only get the knife on the right shoulder
Do a bulltrue in matchmaking to unlock the avatar award.
He is wearing the Commando helmet that you unlock by ranking up.
Commander
5h1t
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.
You have to be an warrant officer in halo reach to unlock the helmet you also have to go to halowaypoint and unlock the armor.
By getting to Leiutenant Colonel rank you unlock the CQC shouloders to buy in the Armory.
probably the haunted helmet but you have to first have 100 percent armory completion for it to become able to purchase (personally i think that the gungnir helmet looks the coolest though)