Unsimulated Sex in Film

is one of the best wikipedia articles in the entire world.  Item #2, Sweet Sweetback's Baadasssss Song, is itself a link to another of the best wikipedia articles in the entire world.  Last on the list--BUT NOT LEAST--is Antichrist:

This film by Lars von Trier features a scene of penetrative vaginal intercourse, and also includes graphically violent sexual imagery. Body doubles were used to make the film.