The developers of the award-winning game are thanking you with new threads for your comprehensive Batman Simulator.
Over on the Arkham City community page, Rocksteady announced that starting tomorrow, December 21st, players will be granted a free Batman, Inc. costume as a token of the developer's gratitude for helping the game sell like crazy over the last two months. From the post, it's not clear whether this will be an automatic update or if you'll have to navigate through Xbox Live/PSN/Game For Windows and find this content yourself, but hey, it's free. Game Director Sefton Hill promises more info as soon as the download is available, though.
Not only that, but Rocksteady has also revealed a cheat that will allow you to unlock any skins that you've downloaded without having to complete the game:
We also know you want to deliver justice on the streets of Gotham as Batman in your favorite skin, any time and all the time. So using the below cheat, you can select any alternative Batman skin and play them in the main game, without having to complete the full game.
To unlock this, simply press the following combination on the Main Menu screen (after you have selected your save slot):
Left, Left, Down, Down, Left, Left, Right, Up, Up, Down.
You will get an audio confirmation and when you continue your game, you will get the option to select your favorite skin.
Here's what the Batman, Inc. skin looks like in action (along with the game's other costumes):