- Bare-Bones team Deathmatch
- Hardcore HQ
- Multi-Bomb Search and Destroy
- Hardcore FFA
360 Fanboy described them perfectly:
Harcore HQ and FFA are fairly self-explanatory, as they are simply more hardcore versions of standard gametypes. They include higher damage and no HUD, so tactics are key. Multi-Bomb Search and Destroy, unsurprisingly, gives all memebers of the attacking team a bomb for their planting pleasure. Bare-Bones Team Deathmatch may be the most intriguing of the bunch, as it removes all perks and kill streak rewards. In other words, you can't blame all your deaths on enemies that poop grenades when they die.
These playlists are in testing so I have no idea when they will be publicly playable.

COD 4's Newest Logo