Actually you don't unlock armor you unlock different characters and their armor. In order to do this you must complete the story of the game. Do this on any difficulty to unlock all the characters except Dare and her Recon Helmet. She is unlocked through the completion of the game on legendary.
You unlock the odst armor by unlocking the UNSC SPARTAN achievement
To get the recon armor you have to complete all the vidmaster achievements in halo3 and halo3 odst.
The Vidmaster Challenge is an Achievement that you have to unlock so you can get Recon Armor when Halo 3: ODST comes out.
you have to complete halo 3 odst on legendary, have xbox live and complete halo 3 on legendary
The only way to get armor on ODST is to unlock it on campaign . Except recon wich you need Halo 3. By Mr. Happy Guy.
All in halo 3 and all in Halo 3 ODST.
Lucky for you, there is now a way to easily unlock recon armor. There are a few steps you must complete to unlock Recon armor in Halo 3. 1. Buy Halo 3: ODST 2. Create a bungie account. 3. Complete the vidmaster achievements on Halo 3 and Halo 3: ODST. There are 7 in all. 4. Under your account preferences, click Unlock Recon. You should now have recon armor. RUB IT IN THEIR FACES!!!
Unlock Halo 3:ODST's Campaign Complete Achievement. Once you beat the ODST campaign, visit Halo Waypoint on the dashboard to unlock the item.
ODST and Mark V armor are the ones.
White
you get all the vidmaster achievements on halo 3 and halo 3 odst
unfortunately without mods, it cannot be unlocked :L