Just picked up Braid for the mac.
Oh my god it's awesome.
It's also damn annoying, but for about £7 - so so worth it.
If you haven't tried/heard about it, it's originally an XBox 360 Live Arcade Game, then ported to the PS3 and the PC/Mac. In it you play a guy called Tim who's rescuing a Princess he lost through a mistake. The gameplay is essentially platforming puzzle-tastic, but crucially each level is a puzzle where you manipulate time to achieve the result and each world has a different mechanism. I'm yet to finish it, and I've been playing pretty hard over the last few days. Often the puzzle answers are clear but how to effect them is not!
Probably the best game I've played in ages, including things like Modern Warfare 2 and GTA 4...
Buy it, you will definitely NOT regret it.