Rockstar announced in their press release today that select US and UK retailers will offer a variety of pre-order bonuses.

These bonuses include: The Referendum, which you can currently vote to choose one of three in-game outfits that will be awarded as part of the pre-order bonus. Voters also get a crack at daily $100 GameStop gift cards or possibly a trip to the Grand Canyon. (Grand prize)

The Golden Guns, allowing you to aquire more fame and thus making more in-game side missions available. Specific to Amazon pre-orders, who will also receive a $10 Amazon gift card

The War Horse, I can only speculate this is for in-game travel as the description was a bit vague. This is specific to Best Buy for US and HMV in the UK.

For more information please visit: http://www.rockstargames.com/reddeadredemption/preorder