To unlock the Recon Armor, you must unlock the following seven "Vidmaster challenge" achievements in Halo 3 and Halo 3: ODST. After you complete the achievements, visit Bungie.net to get the download code. The following are the Vidmaster achievements:
Halo 3 Vidmaster Challenge achievements ACHIEVEMENT - HOW TO UNLOCK Vidmaster Challenge: Annual - Complete Halo on 4-player Legendary LIVE co-op, with Iron, and everyone in Ghosts. Vidmaster Challenge: Lightswitch - Get the rank of Lieutenant in any playlist in the new EXP progression system. Vidmaster Challenge: 7 on 7 - Entered into a ranked or social playlist with 7 EXP on the 7th of the month. Vidmaster Challenge: Brainpan - Find all the hidden skulls on the Mythic maps.
Halo 3: ODST Vidmaster Challenge achievements ACHIVEMENT - HOW TO UNLOCK Vidmaster Challenge Classic (25 points) - Finish any level solo on Legendary, on LIVE, with no shots fired or grenades thrown. Vidmaster Challenge Endure (25 points) - In Firefight, on any mission, pass the 4th Set on 4-player Heroic LIVE co-op. Vidmaster Challenge Déjà Vu (25 points) - Beat Highway on 4-player Legendary LIVE co-op, with Iron, and no 'Hog or Scorpion.