Halo 3 Armor Permutations - Guide for Halo 3

All armor in Halo 3
(If you must beat the campain , you get the chest on Tvaso Highway, shoulders 
on the Ark, and head is the entire campain on required difficulty.

Spartan
Mark VI- Starter
CQB- Starter
Eva- Beat campain on Normal
EOD- Beat campain on Legendary
Hayabusa- Collect all skulls. (See Halo 3 Skulls by Evil Monkey 13)
Katana- Get 1000 gamerscore.
Security- Get 1000 gamerscore.
Recon- Complete all vidmaster challenges in Halo 3 and Halo 3 ODST
Scout- Too Close to the Sun, Mongoose Mowdown, and Used Car Salesman
ODST- Become a Spartan Graduate online
Mark V- Become a UNSC Spartan online
Rogue- Become a Spartan Officer online.

Elite/ Sangheili Armor
Combat- Starter
Assualt- Starter
Flight- Complete campain on Heroic
Ascetic- Up Close and Personal, Overkill, and Steppin' Razor
Commando- Triple Kill, Halo 3 updates/ Steppin' Razor, and Overkill.

Shipmaster- Does not exist as an elite armor. Though to look similar to one 
have Assault Shoulders, Combat Head, and Flight Body,