You might have picked this up or you might have not, but something of a jewel has just been released on Steam. It's called Dear Esther, and the main purpose in the game is to walk. You journey along a trail on an island to the west of Scotland, whilst every now and then a narrator speaks to 'Esther.' In short, that's the 'game'. While you walk around in gorgeous and heavily atmospheric landscapes, your mind starts boggling at what you see, and what the narrator tells you.
The environments are beautiful, and the way it taps into emotions of sadness is a new unique thing for the medium. I highly recommend you give it as shot, since it's only 10 bucks on Steam. My best 10 bucks of the past half decade.
I can't give you an links to trailers or screen shots since this is actually my first post and the 5 days-no-links haven't yet passed, nor is this some sort of commercial act. I simply loved playing it, and by sharing hope you'll enjoy it as well.