Armor customization

Armor Permutations are a feature in Halo 3, allowing the player to aesthetically customize their multiplayer character, the armor, however, doesn't have any effect on gameplay, only cosmetic changes. The feature allows players to change the helmet, pauldrons, and torso armor worn by their multiplayer avatar.

SPARTAN Armor Permutations
There are a wide variety of SPARTAN II armor permutations, with eleven helmets, eight shoulder pieces, and eight chest pieces for a total of 5,632 different SPARTAN II armor permutations: one helmet, two shoulder pieces, and one chest piece per permutation, not including the Bungie Armor chest armor, and taking into account the Rogue, Mark V, and ODST Armor, which only have helmet pieces; and Security Armor, which HAS A KATANA CHEST PEICE. The HAYABUSA Project, developed alongside the MJOLNIR Project, includes the HAYABUSA and Katana permutations.

Players without XBOX Live can unlock the following permutations:


 * Full Hayabusa armor (find all skulls)
 * Full EOD (Legendary completion)
 * Full EVA (Normal completion)
 * Security (Shoulders)
 * Scout (Helmet and Chest)

Helmets

 * Mark VI: Unlocked by default.
 * CQB: Unlocked by default.
 * EVA: Unlock the Campaign Complete: Normal Achievement.
 * EOD: Unlock the Campaign Complete: Legendary Achievement.
 * Hayabusa: Collect all 13 Skulls in Campaign mode.
 * Security: Get 49 Achievements
 * ODST: Unlock the Spartan Graduate Achievement. After TU2, in the new rank progression system this Achievement must be unlocked by reaching the rank of Private grade two in any playlist ranking.
 * Mark V: Unlock the UNSC Spartan Achievement. After TU2, in the new rank progression system this Achievement must be unlocked by reaching the rank of Sergeant in any playlist ranking.
 * Rogue: Unlock the Spartan Officer Achievement. After TU2, in the new rank progression system this Achievement must be unlocked by reaching the rank of Lieutenant in any playlist ranking.
 * Recon: One way is to unlock all of the Vidmaster Achievements in Halo 3 and Halo 3: ODST. The problem is that for the achievement, "Brainpan," you must find the skulls on all 6 Mythic Maps, however, some will be released with Halo 3: ODST, meaning that players must wait until the release of the game to get the achievement. The armor can also be unlocked by achieving something that makes Bungie feel you deserve it, such as Forge a map, make a screenshot or machinima, or win against Bungie in a Bungie vs. World event.
 * Scout: Complete the Used Car Salesman Achievement.

Shoulder Pieces

 * Mark VI: Unlocked by default.
 * CQB: Unlocked by default.
 * EVA: Complete The Ark in Campaign on Normal or higher difficulty.
 * EOD: Complete the level The Ark on Legendary difficulty.
 * Hayabusa: Collect at least 9 skulls.
 * Security: Earn 35 Acheivements
 * Scout: Complete the Mongoose Mowdown achievement.
 * Recon: Get all the Vidmaster Achievements in Halo 3 and Halo 3: ODST. It can also be unlocked by doing something that makes Bungie feel you deserve it, such as a Forge map, film, or screenshot, or participating in a Bungie vs. World Event.

Chest Armor

 * Mark VI: Unlocked by default.
 * CQB: Unlocked by default.
 * EVA: Complete The Tsavo Highway on Normal difficulty or higher.
 * EOD: Complete The Tsavo Highway on Legendary difficulty.
 * Hayabusa: Collect at least 5 skulls in campaign.
 * Katana (Add-On): Unlock at least 49 achievements which are worth 1000 or more Gamerscore points in Halo 3. NOTE: There are reports from people who get it with less achievements. Since the release of the mythic map pack the Katana seems to unlock for those that download early(without the need for 1000 gamerscore OR 49 achievements)
 * Scout: Unlock the Too Close to the Sun Achievement, although has been reported that it may appear later sometimes.
 * Recon: Get all the Vidmaster Achievements in Halo 3 and Halo 3: ODST. It can also be unlocked by doing something that makes Bungie feel you deserve it, such as a forge map or screenshot and also winning a contest or various competitions that Bungie composes.
 * Bungie: A popular misconception is that the Bungie Flaming Helmet is actually a helmet mostly perceived as Hayabusa, but in fact, it is a piece of fire on the collar. Thus, it is a chest piece. It is the Bungie Chest Piece that allows the flame on the head which can be used with any helmet and shoulder piece. The only way to get it is to get hired at Bungie.

Sangheili/Elite 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 15 different Sangheili armor permutations: one helmet, two shoulder pieces, and chest piece per permutation and 625 possible combinations with all pieces in consideration.

Helmets

 * Combat: Unlocked by default.
 * Assault: Unlocked by default.
 * 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: Unlocked by default.
 * Assault: Unlocked by default.
 * Flight: Complete the level The Ark on Heroic or Legendary difficulties.
 * Ascetic: Unlock the Overkill achievement.
 * Commando: Unlocked by default after Auto Update 1 was applied on February 19, 2008. At first, the Steppin' Razor achievement was needed to unlock the shoulder pieces, but a bug prevented this. Some people reported getting the shoulder pieces, but then they re-locked themselves after a certain amount of time without being used.

Chest Armor

 * Combat: Unlocked by default.
 * Assault: Unlocked by default.
 * 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.

Trivia

 * There was originally going to be an Arbiter Armor Permutation, but it was taken out before Halo 3's release. Bungie however, did not explain why.
 * The neck of an Elite (regardless what armor permutation used) is completely immune to any form of damage, except for a charged Type-25 Directed Energy Pistol. In addition, the projectile will simply pass through the neck, as though the neck wasn't there, without even a blood spatter. This is because both Elites and Spartans share the same hitbox (i.e. where you can hit the character), but have different models.