Halo is rapidly becoming a tradition at MS. All over the company XBOX's are being setup with the sole purpose of playing halo. Many teams have their rig subsidized by their morale budget. We on the Windows Forms team wanted a more exclusive experience, so we started an XBOX membership program. Its like a country club, except without the golfing.
Team High Life also has a standing halo tradition. We've convened on just about every Wednesday night in building 50 since the magic evening of 11/15/01. Playing with the Windows Forms team, on a single box is a blast, but there is nothing quite like 4 box, 16 way action. Ask ChrisAn, he shows up from time to time.