If you pre-order your Special Edition copy of Red Dead Redemption from GameStop you'll bag yourself The Deadly Assassin Outfit. It won the public vote by a mile over the other two choices - The Savvy Merchant Outfit & The Expert Hunter Outfit.
Don't expect to just load the game up and find yourself invincible though, you'll need to complete these missions first to unlock the outfit.
Win A Duel In Armadillo
Travel to the town of Armadillo, and accept any
challenge to fight a duel. Just make sure to win.
Capture Or Kill Mo Van Barr
(He's the winner of the 'Movember' Competition)
While in Armadillo, find the wanted poster for Mo Van
Barr, accept the Bounty Hunting mission, and bring
this notorious member of the Walton Gang to justice,
dead or alive.
Solve The Mystery Of The Missing Townsfolk
People have been disappearing for weeks from the
outskirts of Armadillo. Track down the clues, solve
the mystery and live to tell the tale.
Search Coot's Chapel
Find the ruins of Coot's Chapel in the wilds of Cholla
Springs, and search for treasure.
Complete The Twin Rocks Hideout
Find the legendary criminal hideout of Twin Rocks,
located North of the town of Armadillo to complete
this final challenge.