:the game: game and its sequels are some of my all-time favorite games. It's browser-based, no download and free.
The first few games: the objective is simple. You're placed on a grass platform in the middle of the air. Objective? Fall off. Just walk off and die. There are many more things that come up later, and each level is concluded with an ironic and funny pun. Also, a bit bloody, but it's all very fake. However, the final game (Reimagining :the game: game) is so much more revamped and difficult, I'm still trying. No more is the grass platform. There are much more difficult levels, so beware! I highly recommend it, it's so punny and yet a very satisfying game experience.