Looks like the 'MP Bomb' that Bungie teased yesterday did relate to a multiplayer mode. More specifically, the date in which we'll all be playing the Beta of Halo: Reach - 3rd May 2010. Those who have Halo 3: ODST will already have an invite.
The video released displays a whole host of multiplayer modes that we can expect from the Beta, including Invasion and Headhunter. There's an awful lot of sharpshooters and assassinations going on too.
Oh, and there are jetpacks. Lots and lots of jetpacks. It certainly looks mad, and we can't wait for the Beta to drop and have a little play ourselves. Check the video below and watch as your calendar doesn't go fast enough for that 3rd May date.