If you pre-order Batman: Arkham City from Best Buy you can unlock a playable Tim Drake Robin character for the game.

From the press release:

    Pre-Order at Best Buy North America for Exclusive Access to the Robin Pack!

    Warner Bros. Interactive Entertainment and DC Entertainment today confirmed that Robin will be a fully playable character in the new and improved challenge mode in Batman: Arkham City. The Tim Drake Robin pack is currently available exclusively to North American fans who pre-order the game from Best Buy on any of the platforms for which the game will be available: Xbox 360® video game and entertainment system from Microsoft, Games for Windows PC and the PlayStation®3 computer entertainment system.

    Robin will come complete with his own unique gadgets and special moves, and will be playable in all challenge maps in the game, as well as two additional challenge maps that are included with the pack – Black Mask Hideout and Freight Train Escape. The pack will also contain a bonus Red Robin character skin.