Earlier this week, Bungie said it would be "dropping a multiplayer bomb". It appears a Taiwanese site has dropped that bomb a little early, with the leak of what looks a lot like a new trailer for the game.
Now, this may be an elaborate hoax, but if it is, it's a cruel one. Because this looks like a pleasant step up from Halo's current multiplayer system. Stab moves, jet packs, plenty of explosions...yeah, this is nice.
Bear in mind, even though it looks slick, you can never be sure it's real. Then again, it might also be a "release" on the part of Bungie disguised as a "leak". You never know these days.
Update: It's official, Bungie just released it on their site.