0rbitalis is the most obtuse game I've ever played, and I love it. 

Perhaps I should explain: 0rbitalis is an abstract gravity-puzzle game. The object is to keep your tiny red dot orbiting on screen as long as possible, arcing it around planets and stars (represented by larger and smaller abstract shapes) as it swirls and whirls around the screen. While you only have to do so for a very short set amount of time, there are online leaderboards that encourage players to keep their orbits going for as long as possible, with some frankly unbelievable times in places.