I don't use the mac for playing games anymore (since I've bought an xbox, yay) but I know the games I'm going to list are available for mac too. I've enjoyed Rage very much. Skyrim is an epic game that works wonderfully with it's unofficial port (tried on a MacBook Pro 15"). Also I'd suggest Deus Ex: Human Revolution once it comes out, it's absolutely my favourite and the most epic game ever made IMHO