CrossOver Games, a games-specific version of CrossOver, their Windows emulation software. Jeremy White has the story behind the release over on their blog -- apparently the application team wasn't working quite as quickly as they wanted, but the games team was chugging right along in terms of compatibility, so they decided to go ahead and ship what they'd done with games on its own.
The compatibility list isn't bad (most of the Steam stuff is on there, which is great, although it is a little weird that they brag about World of Warcraft and EVE Online, considering that those two run natively on Mac just fine; guess you Linux folks need your MMO fix, too) but nothing really jumps out here that might encourage you to use CrossOver rather than just, say, Boot Camp-ing the game up yourself. DirectX 10 is apparently causing problems, too, since neither Crysis, Gears of War, or Unreal Tournament III are on there.
Still, a valiant effort, and if you're desperate to get one of these games working and playable on your Mac (and don't have a spare copy of Windows sitting around to install with Boot Camp), CrossOver Games might be just what you need. TUAW is working on getting a copy of it, and as soon as we do, we'll run it through the grinder and see what we can get to come out the other side.