pulled off of Xbox Live Arcade over a year ago because of "expiring rights" (i.e. Zenimax acquired Id Software)? Do you also remember that Zenimax stated that the game would be back up "soon," courtesy of Bethesda? Well then, good news because "soon" is apparently today! Bethesda has sent out a note announcing that the original Doom has returned XBLA.
The granddaddy of modern shooters will set you back $5 and features both co-op and versus multiplayer via Xbox Live.