The latest playlist update brings the mode Team SWAT and FFA SWAT to Halo: Combat Evolved Anniversary. This might not sound like a big deal, but this is the first time that SWAT has been available in original Halo game. It's been featured in most of the Halo sequels, but never the first game.
You can now find out for yourself how SWAT plays in the original Halo. The matchmaking gametype is currently available for both PC and Xbox One in Halo: The Master Chief Collection.