A game that has quite possibly the most interesting gameplay ever. Portal is a first person shooter, with a twist. You don't kill people, and it's more like a puzzle game than anything. It was released as one of the 5 games that come in the Orange Box which was released last fall, and was released as a stand-alone game just a month ago.
For those who don't know, Portal is a puzzle game where you play as the test subject in a lab who has to complete many obstacles that slightly increase in difficulty after each level. You are given this really awesome portal gun that shoots two portals that are linked together. So if you shoot a portal at the wall in front of you and shoot a portal at the wall above a platform two stories up, you can walk through the portal you shot on the ground floor wall and step onto the high platform. I can't really explain it in any other way. But this teaser trailer pretty much explains it all.
http://youtube.com/watch?v=TluRVBhmf8w
