Journey on the Playstation Network is an incredibly beautiful little game. It is another one that will be referenced alongside Ico & Shadow of the Colossus in the arguments as to whether or not games classify as art. (They are)
You start the game as a lone nomad sat in the middle of a desert and other than instructions on how to move the camera and yourself you are told nothing. You are left to explore on your own with the only guide being some markers on the top of a dune.
When you reach them you see a glowing mountain and your whole game is about reaching that point. Along the way you will bump into other Nomads, that turn out to be other players running around in your game seamlessly.
It is worth buying because as well as being a very good game, it is one that every gamer must experience