There are two main types of armor available in Halo 3. They are the Spartan and Elite body type. However, take note that you can customize your appearance but you will only be able to see them in multiplayer mode. Most of the armor can only be unlocked when you  achieved certain requirements. Once unlocked, you can mix and match the head, shoulders and body armor.

   

By default, there are two Halo 3 Elite Armor sets - Combat and Assault, which are already unlocked. The Elite Combat armor head is very angular in shape and has a set of spikes at the back of the helmet. Each side of shoulder armor has a triangular plate, which points upwards. The Elite Assault armor is more rounded in shape and the helmet completely covers the head. The shoulders armor has a rectangular plate on the edge of each shoulders.

The Halo 3 Elite Armor consist of 3 unlockable sets namely  Flight, Ascetic and Commando.

To Unlock the Halo 3 Elite Armor :

Flight (Helmet)   : Complete Campaign mode on Heroic

Flight (Shoulder): Complete The Ark on Heroic or Legendary

Flight (Body)       : Complete Tsavo Highway on Heroic or Legendary

Ascetic ( Helmet)  : Get the “Stepping Razor” Achievement

Ascetic (Shoulder): Get the “Overkill” Achievement

Ascetic (Body)       : Get the “Up Close and Personal” Achievement

Commando ( Helmet)  : Get the “Overkill” Achievement

Commando (Shoulder): Get the “Killing Frenzy” Achievement

Commando (Body)       : Get the “Triple Kill” Achievement

All the achievements listed above have to be obtained online in any free for all playlist.

Stepping Razor Achievement:  To get this achievement you have to kill 3 enemies with an Energy Sword, within 4 seconds of one another.

Triple Kill Achievement: Kill 3 enemies within 4 seconds of each kill.

Overkill Achievement: Kill 4 enemies within 4 seconds of each kill.

Killing Frenzy Achievement: Kill 10 enemies without dying.