When talking about movie posters, one can't avoid talking about Quentin Tarantino. Truly, it's hard to pick out just one of his movies for an example of a great poster. Kill Bill was bright and bold. Reservoir Dogs has become an icon on the walls of frat rooms the world over. I've always loved Pulp Fiction, though. It is an interpretation that seems obvious, but considering the number of obvious movie posters that get ignored every year in modern Hollywood, perhaps obviousness is not something that is very... obvious.
Every element of the film is represented in the poster. The nostalgia, the sex, the violence, even the attitude of the film is represented in Uma Thurman's face. Very few movie posters are this perfect.