To get the recon armor you have to complete all the vidmaster achievements in halo3 and halo3 odst.
when get achievements (like beating the game on Legendary or finding all the skulls) you can unlock some of the armor.
49/49 not including recon.
Complete all aspects of the game required to unlock each type of armor. You can google a list of these actions. Recon is now an un-lockable armor as well, complete all "vidmaster" achievements.
You can unlock all the armor by competing Halo 3 achievements. The achievements linked to the downloadable map packs are generally easier to complete and give more gamerscore, therefore giving the armour faster.
To acquire the "Katana" armor permutation chest-piece, you must unlock all Xbox 360 achievements, or receive 1000 Gamer Score from other achievements (Mythic Map Pack I and II, Heroic Map Pack, etc.)
As of now, it's 79. And Bungie will probably award you with something. Do you already have katana and marathon man armor?
To get security armor in Halo 3... all you have to do is get all of the original 49 achievements (you don't need the new mythic or legendary achievements).
No, in Halo 2 you can not unlock armor.
you need to achieve all the achievements. you need to achieve all the achievements.
you have to get all vidmaster achievements to get recon.
To get the Katana as an armor permutation in Halo 3, you need to get 1000gp in the game. The new achievements released for Halo don't affect it. The easyst way to get it is to get all the "old" achivements.