Although I wasn't a great fan of the movie, the trailer for BUFFALO 66 is amazing. It's on the dvd and although I watched it after the movie I guess you could watch it safely beforehand.
I've always loved the trailer for The Fifth Element. The cuts and the music and the overall visual impact mesmerized me when I first saw it. Of course the Episode I and II trailers sent chills up my spine just because they were Star Wars (not being aware at the time of the flaws in either movie). Actually, the new trailer for Star Trek Nemesis seems totally cut from Lucasfilm cloth. For the first 2/3 (characters aside) you would swear it's a trailer for a Star Wars film.