While the rumor mill caught wind of this one a little earlier than Nintendo anticipated, Mario Maker was officially announced for Wii U. This looks like a full-featured level creator, not only with the classic Super Mario Bros. style, but the ability to create stages in the New Super Mario Bros. U look as well. I'm definitely interested to see how this shapes up, and can't wait to get my hands on it. Check out the trailer below.
UPDATE: Screenshots added.