Currently I'm playing Quantum Conundrum on Windows, which is really addictive. It's somewhat of a Portal 2 ripoff (which is already one of my favorite games), but instead of portals you work with different dimensions in solving puzzles, a dimension where everything is 10 times lighter and a dimension where everything is 10 times heavier, etc.
It's by Square Enix and available on Steam.
And I'm playing Trine 2 on OS X. Damn, that's a beautiful game. The graphics are sublime, controls are perfect and it's a real original story. I never played the first game, but I read everywhere that this one is a better update.
It kinda reminds me of Lost Vikings, working with a team of three characters getting through medieval levels.