Although the controls are really rough (it really should be point-and-click instead), it's still an intriguing story in an interesting environment.

Team Fortress 2 [Steam store page]
I wanted to love this game, but found it hard to get into because it requires team effort (mainly a healer at your back) or you die exceptionally fast. Unlike Unreal Tournament or Counter-Strike: Source where you can easily play a quick lone wolf match

Machinarium [Steam store page]
Nicely drawn point and click - but the puzzles are too obtuse for their own good. The hint button is hidden behind a long minigame with a key that shoots bullets (which the game doesn't mention and the minigame can't be completed without them)