Armor Permutations

Armor Permutations are a feature in Halo 3, Halo 3: ODST, and Halo: Reach which let players customize their multiplayer character's armor to their liking. In Halo 3, this feature allows players to change the helmet, shoulders and chest armor pieces worn by their multiplayer character. Players also have the option of choosing between being a Spartan or Elite in multiplayer.

SPARTAN Armor Permutations
There is a wide variety of SPARTAN II armor permutations in Halo 3. Eleven helmets, eight shoulder pieces and eight chest pieces for a total of 5,632 different SPARTAN II armor permutation possibilities: One helmet, two shoulder pieces and one chest piece per permutation, not including the Bungie Armor Chest piece. It should be noted the Rogue, Mark V, and ODST armor only have helmet pieces and Security armor has both helmet and shoulder pieces but is in the absence of a chest permutation. The HAYABUSA Project includes the HAYABUSA and Katana permutations.

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 625 different Elite armor permutations: One helmet, two Shoulder pieces, and one Chest piece per permutation.

ODST Permutations
Halo 3: ODST features armor customization, though it is not as complex as Halo 3 ' s. One can play as each member of the squad having their own unique aesthetic armor. Players can choose primary and secondary armor colors, but the armor's main color remains the same. Players can also choose not to wear a helmet unless they are using the Rookie character model. Choosing not to wear a helmet does not affect game play. Without a helmet, the player still has the same health and stamina and they can still use VISR mode.

Characters

 * Rookie: Unlocked by default.
 * Dare: Complete the Campaign on Legendary.
 * Buck: Unlock the Tayari Plaza Achievement.
 * Dutch: Unlock the Uplift Reserve Achievement.
 * Romeo: Unlock the NMPD HQ Achievement.
 * Mickey: Unlock the Kizingo Boulevard Achievement.
 * Sergeant Johnson: Came with pre-order of Halo 3: ODST.

Reach permutations
Halo: Reach offers a new and more advanced armor customization system that allows players to add several parts on top of their general armor. By winning or finishing matchmaking games, getting achievements, commendations or by completing daily and weekly challenges players will be able to earn "credits" (cR) which will allow them to purchase new armor. All of this will be available in the Halo: Reach Multiplayer Beta.

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 armor was though going to be released as a DLC but was scrapped due to coding conflicts.
 * 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 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.
 * Each Elite also has a modified neck, whether sleek black, or a different model such as scale-like plating at the back.
 * Halo: Reach features a new armor permutation system that has a player's multiplayer armor layout and colors be used on Noble Six in the Campaign mode. However, playing as an Elite in Multiplayer will not make Noble Six an Elite in campaign.
 * Reach also grants players the ability to add various accessories to their armor, such as flashlights and bandoliers, which affect aesthetics only.