Possibly Avengers 2: Age of Ultron Teaser Trailer?
http://www.youtube.com/watch?v=QZVbRfO0hik If it is fake then they went through hell to make it look like it wasn't. You decide.
http://www.youtube.com/watch?v=QZVbRfO0hik If it is fake then they went through hell to make it look like it wasn't. You decide.