Since the last two games I looked at have been shooters, I decided to change it up today and look at puzzle game today.
Fireboy and Watergirl (Originality is rich in game titles these days) is a very interesting game to say the least. You control two characters at the same time. Watergirl with the WASD keys and Fireboy with the Arrow Keys.
Its a 2D platform puzzle game. Try saying that five times fast.
You have to maneuver Fireboy and Watergirl around the map over obstacles to collect gems and get yo their doors. Your score is based off the time it took you and how many gems you get. A simple enough concept if you were to use one character, but using two characters at once adds a whole extra element.
Really worth a try, if you're a masochist like me.