Tonight I played World of Goo. This is a puzzle game, in the vein of Lemmings. Your aim is to get your Goo Balls to the end of the level, using them to build structures to get there.
World of Goo
Each level has different challenges, with a variety of type of Goo Balls. It can get challenging, since your structures are flexible and tend to sway as they get taller. It's a pretty addicting game and there is a hidden challenge, called OCD, if you manage to rescue the maximum number of Goo Balls.
Definitely a game worth picking up.