Darrk Assassin
CAG Veteran
via MajorNelson's twitter. If you buy bioshock 2 for $37.99 (download - 25% off) and the DLC for 400 MS points, you will receive 800 MS Points free.
http://www.microsoft.com/games/en-us/games/Pages/sales.aspx
http://www.microsoft.com/games/en-us/games/Pages/sales.aspx