50.
Night of the Iguana
1964
By IFC on 06/25/2009 
This is IFC.com's list of the 50 Greatest Trailers of All Time:
Night of the Iguana (1964)
It's only fitting that this list ends (or begins) with the trailer for John Huston's 1964 adaptation of the Tennessee Williams drama starring Richard Burton, Ava Gardner and Deborah Kerr. In spite of those marquee names, it was the far lesser-known Andrew J. Kuehn that made the film a landmark in cinema history by introducing innovations in movie trailer-making that remain a staple today.
Hired by MGM after excelling at cutting trailers for foreign films in the early 60s, Kuehn took pre-film advertising to a whole new level when he employed a young James Earl Jones to do an omniscient voiceover, added a jazzy score and introduced quick-cut editing in a world where trailers were usually comprised of full scenes. Today, the Night of the Iguana trailer looks a bit like avant-garde filmmaking, but it proved the basis for the rest of Kuehns influential body of work, including trailers for Taxi Driver, Alien and Jaws, as well as the entire business of film marketing. They should be called leaders.
We know them as trailers, but they don't trail anything; they play before the movie, not after it. The name dates to their earliest incarnation, when they actually did follow the feature.
~ NICHOPOULOOZA