Armor customization

An Armor Permutation is a feature in Halo 3, allowing custom modifications to both Human Spartan and Elite (Sangheili) Armor systems.

Background
Originally discovered in the Halo 3 Beta code by modders, Halo 3's new multiplayer armor permutations provide high levels of player customization and were confirmed by GamePro's June issue.

It was confirmed by Bungie, that 2 SPARTAN and 2 Elite variant armors are given at the start of Halo 3. For SPARTANs, this includes the MJOLNIR Mk. VI armor, and the CQB (Close Quarters Battle) permutation, and for the Elites, the Combat and Assault permutations are included.

Spartan Armor Permutations
There were 5 permutations for Spartans discovered by modders in the Beta code; Bungie confirmed two before the release of Halo 3: EVA(Extra-Vehicular Activity) and CQB(Close Quarters Battle).

Unlocking
Spartan Armor Permutations are unlocked by completing various campaign levels on different difficulty settings or unlocking various achievements via either campaign or online play.

Helmets

 * Flaming Helmet: Bungie Employees only (verified)
 * Mark VI: Default Unlocked
 * CQB: Default Unlocked
 * EVA: Complete Campaign on Normal, Heroic, or Legendary
 * EOD: Complete Campaign on Legendary
 * Hayabusa: Collect all skulls
 * Security: Earn 1000 out of 1000 Gamerscore Points for Halo 3
 * Scout: Complete "Used Car Salesman" Achievement
 * ODST: Complete "Spartan Graduate" Achievement
 * Mark V: Complete "UNSC Spartan" Achievement
 * Rogue: Complete "Spartan Officer" Achievement

Shoulder Armor

 * Mark VI: Default Unlocked
 * CQB: Default Unlocked
 * EVA: Complete The Ark on Normal, Heroic, or Legendary
 * EOD: Complete The Ark on Legendary
 * Hayabusa: Collect 9 skulls
 * Security: Earn 850 out of 1000 Gamerscore Points for Halo 3
 * Scout: Complete "Mongoose Mowdown" Achievement

Body Armor

 * Mark VI: Default Unlocked
 * CQB: Default Unlocked
 * EVA: Complete Tsavo Highway on Normal, Heroic, or Legendary
 * Hayabusa: Collect 5 skulls
 * Katana (Add-On) : Earn 1000 out of 1000 Gamerscore Points for Halo 3
 * EOD: Complete Tsavo Highway on Legendary
 * Scout: Complete "Too Close to the Sun" Achievement

Elite Armor Permutations
The Elite player model also has different armor variations. Elite armor types: A couple of images of the Elite permutations exist below,

Unlocking
Elite Armor Permutations are unlocked by completing various campaign levels on different difficulty settings or unlocking various achievements via either campaign or online play.

Helmets

 * Combat: Default Unlocked
 * Assault: Default Unlocked
 * Flight: Complete Campaign on Heroic or Legendary
 * Ascetic: Unlock "Steppin' Razor" Achievement
 * Commando: Unlock "Overkill" Achievement

Shoulder Armor

 * Combat: Default Unlocked
 * Assault: Default Unlocked
 * Flight: Complete The Ark on Heroic or "The Storm" on Legendary
 * Ascetic: Unlock "Overkill" Achievement
 * Commando: Unlock "Killing Frenzy" Achievement (Still Bugged as of 10/03/07)

Body Armor
Unlock all achievements
 * Combat: Default Unlocked
 * Assault: Default Unlocked
 * Flight: Complete Tsavo Highway on Heroic or Legendary
 * Ascetic: Complete "Up Close and Personal" Achievement
 * Commando: Complete "Triple Kill" Achievement
 * Ninja Gaiden Sword: wiki page

Trivia

 * The armor permutations are completely cosmetic; they cause no change in gameplay.
 * Bungie has stated that there are "thousands" of possible combos, but they refuse to state exactly how many variations will be in the final product, including downloadable content.