In a blog post on May 10th, Valve released the authoring tools for Portal 2 to the public. This means that fans can now make their own Portal 2 maps, skins, models, sound effects and music. I think this officially makes Portal 2 my top game for 2011. Of course, this does mean that for every amazing fan made map, we’ll probably see 5 god awful pieces of crap and 10 phallic shaped maps.
Here's the official announcement.