The Deadly Assassin Outfit is only available to those who pre-ordered Red Dead Redemption from a participating store like Gamestop. While wearing it, your Dead Eye will regenerate twice as fast as normal.
There is still a process to go through to accomplish it, though. You'll need to find five scraps to complete it.
- Scrap 1 is found inside a chest in Coot's Chapel.
- Scrap 2 is yours after you clear out Twin Rocks Hideout.
- To get Scrap 3, you'll have to capture or kill the New Austin Bounty target Moe Van Barr.
- Scrap 4 is won in a duel in Armadillo.
- Finally, Scrap 5 is unlocked after completing the stranger task "American Appetites."
Page two has the rest of the unlockable Red Dead Redemption outfits, including the Duster Coat, Gentleman's Attire, Legend of the West Outfit, and the U.S. Marshal's Uniform.