Not really, special abilities no, its all for looks
By Playing the game hardout. It works.
For info on Halo 3 armors, go to the following link: http://www.gamefaqs.com/console/xbox360/code/926632.html
by getting certain armors
You have to earn achievements or get skulls.
no just work for the armor
Mark IV is a type of armor in the game: Halo 3. This is a evolvement from the Mark V armor in the previous Halo games; Halo:Combat Evolved and Halo 2. The armor is also called the Mark 6. In the game it is an armor that is worn by the main charecter: Master Chief. In the multiplayer game it is an armor that you automaticaly wear in the matches.(there are other armors to wear during matches)
Halo 3: ODST is the newest of the two, but not the newest Halo game.
No. Bungie's gives you the armor as an award. You can't cheat the armor, unless you can cheat them.
Halo 3?
you need to acheive different tasks in order to unlock diffferent armor. You also need to get achievements
If you mean the achievements, when you get all (Or Most) of them, You Get The Hyabusa Katana Armor, along with other armors.
it goes halo, halo 2, halo 3, halo 3 odst and soon halo reach will be available