Armor customization

Armor Permutations are a feature in Halo 3, allowing the player to aesthetically customize their multiplayer character.

Introduction
Armor Permutations allow a player to customize his/her multiplayer character as either a UNSC SPARTAN-II or a Covenant Elite by swapping different helmets, shoulder pads, chest armor, and detailed colors (primary color, secondary color, and armor detail). All permutations are aesthetic only and do not change actual gameplay.

They were originally discovered in the Halo 3 Beta hexadecimal codes by modders and were later confirmed to provide high levels of player customization by GamePro's June magazine issue. Calculated together, there are 187,947,000 combinations for the player to choose from.

Armor Permutations are available only in Halo 3 (in the earlier parts there is only Mark VI Spartan Armor and CQB Spartan Armor), and are unlocked by achievements in either the Campaign or multiplayer modes of Halo 3 or by getting the skulls.

SPARTAN Armor Permutations
There are a wide variety of SPARTAN II armor permutations, with 11 helmets, 8 shoulder pieces, and 8 chest pieces for a total of 6,144 different SPARTAN armor permutation combinations: one helmet, two shoulder pieces, and chest piece per permutation.

Helmets

 * Mark VI: Default Unlocked.
 * CQB: Default Unlocked.
 * EVA: Unlock either Campaign Complete: Normal, Campaign Complete: Heroic or Campaign Complete: Legendary achievements.
 * EOD: Unlock the Campaign Complete: Legendary achievement.
 * Hayabusa: Collect all Skulls.
 * Security: Earn 1000 of 1000 gamerpoints in Halo 3. (Unlock all Halo 3 achievements)
 * Scout: Unlock the Used Car Salesman achievement.
 * ODST: Unlock the Spartan Graduate achievement.
 * Mark V: Unlock the UNSC Spartan achievement.
 * Rogue: Unlock the Spartan Officer achievement.
 * Recon: Bungie employees, winners of tournaments/double exp weekends, and those that impress (or amuse) Bungie in any other way.
 * Flaming Helmet: See "Bungie" in Chest Pieces.

Shoulder Pieces

 * Mark VI: Default Unlocked.
 * CQB: Default Unlocked.
 * EVA: Complete the level The Ark on Normal, Heroic, or Legendary difficulties.
 * EOD: Complete the level The Ark on Legendary difficulty.
 * Hayabusa: Collect at least 9 skulls.
 * Security: Earn 750 of 1000 gamerpoints on Halo 3. Due to inconsistency, this armor permutation is not always given at 750, whereas there are some reports that the Security Shoulders need a minimum of 800 gamerpoints, but the official guide to Halo 3 lists the requirements as 750. Even then the armor permutation may appear for a short time and then disappear, as has been reported.
 * Scout: Unlock the Mongoose Mowdown achievement.
 * Recon: Bungie employees, winners of tournaments/double exp weekends, and those that impress Bungie in any other way.

Chest Armor

 * Mark VI: Default Unlocked.
 * CQB: Default Unlocked.
 * EVA: Complete the level Tsavo Highway on Normal, Heroic, or Legendary difficulty.
 * Hayabusa: Collect 5 skulls.
 * Katana (Add-On): Unlock all achievements in Halo 3. (''Note, Katana is a sword on the back of your armor, which is a Hayabusa chest plate. Not a chest plate. )
 * EOD: Complete the level Tsavo Highway on Legendary difficulty.
 * Scout: Unlock the Too Close to the Sun Achievement.
 * Recon: Bungie employees, winners of tournaments/double exp weekends, and those that impress Bungie in any other way.
 * Bungie: Bungie employees. The Piece looks similar to the EOD piece, and makes any Helmet piece beappear to be on fire. The disadvantage is that the flames can be seen with Active Camo on, negating it's use.

Sangheili Armor Permutations
There are a wide variety of Elite armor permutations, with 5 helmets, 5 shoulder pieces, and 5 chest pieces for a total of 625 different Elite armor permutation combinations: one helmet, two shoulder pieces, and chest piece per permutation.

Helmets

 * Combat: Default Unlocked.
 * Assault: Default Unlocked
 * Flight: Unlock either Campaign Complete: Heroic or Campaign Complete: Legendary achievements.
 * Ascetic: Unlock the Steppin' Razor achievement.
 * Commando: Unlock the Overkill achievement.

Shoulder Pieces

 * Combat: Default Unlocked.
 * Assault: Default Unlocked.
 * Flight: Complete the level The Ark on Heroic or Legendary difficulties.
 * Ascetic: Unlock the Overkill achievement.
 * Commando: Unlocked automatically after Auto Update 1 was applied on February 19, 2008. Originally, the Killing Frenzy achievement was needed to unlock the piece, but a bug prevented this.

Chest Armor

 * Combat: Default Unlocked.
 * Assault: Default Unlocked.
 * Flight: Complete the level Tsavo Highway on Heroic or Legendary difficulties.
 * Ascetic: Unlock the Up Close and Personal achievement.
 * Commando: Unlock the Triple Kill achievement.

Unlocking Permutations
Note: The Arbiter's armor cannot be unlocked. 300px All of the armor permutations.

FLAMING HELMET LINK: http://www.youtube.com/watch?v=Il0a_fKuOJQ&feature=related

Trivia

 * Among the most popular helms for the Elite armor classification is the Assault and Ascetic.
 * Among the most popular helms for the Spartan classification is the Security, Rogue, and Hayabusa.