Instructions
Finish all of the levels in the Campaign mode of "Halo 3." Three entire sets of armor are unlocked for beating the game under the normal, heroic and legendary difficulty settings. Playing through the campaign unlocks the Elite Flight, Spartan EOD and Spartan EVA armor sets.
Obtain several achievements for the Elite sets of armor. Getting the "Overkill" and "Triple Kill" achievements earns the Commando armor, while earning the "Up Close and Personal" and "Steppin' Razor" achievements gives the player Ascetic Elite armor.
Collect a hidden human skull in every level of Campaign mode to unlock the pieces from the Hayabusa Spartan armor. The entire suit becomes available after finding all 13 skulls.
Rank up over Xbox Live to earn several of the Spartan helmets. When your rank improves by winning matches, you are rewarded with the ODST, Rogue and Mark V helmet variants.
Unlock the Spartan Scout armor set by earning the "Mongoose Mowdown," "Too Close to the Sun" and "Used Car Salesman" achievements.
Earn a Gamerscore of 1,000 Gamerpoints in "Halo 3" for the Spartan Security helmet. Each achievement in "Halo 3" is worth a certain amount of Gamerscore. For example, "Mongoose Mowdown" is worth five achievement points. The helmet unlocks automatically once you have a total of 1,000 points for "Halo 3."