At Comic Con this year Jon Favreau wowed the audience with two things: the appearance of Harrison Ford at his first ever Comic Con and an extended sequence from the just barely in production Cowboys & Aliens. It was a first contact scene, where alien spacecraft attack a Western town and only the imprisoned Daniel Craig, wearing a mysterious alien doohickey on his arm, could stop them.
That scene (and what leads up to it) forms the backbone of the excellent first trailer for the film. It doesn't give away much - we barely even see the alien spacecraft - but it does show off the film's ass-kicking tone and the way it treats the Western genre completely straight. I am very, very excited for this movie.