The classic FPS DOOM, which is available for about every platform ever conceived, is headed back onto the Xbox 360 tomorrow morning. On January 20th the game will be republished to the Xbox Live Arcade Marketplace.
DOOM was originally released for XBLA in September of 2006, and was published by Activision, but when Bethesda bought iD Software, it had to be taken down. The publishing is now being done by Bethesda itself.
Remember that while the game is old, this port has online Deathmatch and Co-Op, which I personally think is a complete blast to play and certainly makes the game worth its 400msp ($5) asking price.
The 1993 classic was one of the first first-person-shooter games ever and inspired years of DOOM-Clones until the modern FPS design came about. The game is rated M for Mature, though its violence hardly compares to most other current games.