Instructions
Start "Halo: Reach," and go online. Join a multiplayer game, such as match-making or firefight. Every online game you participate in earns you credits, which you can then use to purchase helmets.
Go to the online store by clicking on the "Armory" link between battles. Here, you can spend your hard-earned credits on new helmets. The cheapest ones cost 500 credits, while the more expensive JFO model runs a whopping 60,000.
Purchase every helmet in the game to unlock the fabled Haunted helmet, which looks like a Skeletor mask from "He-Man." Once unlocked, the Haunted helmet costs only a single credit. Gaining access to it, however, costs nearly one million.