Full frontal nudity.
As titillating as the phrase may sound, baring it all on screen is not always a sexy endeavor. Truth be told, nudity can be as frightening for an audience as it is for the thespian tasked with dropping trou (see The Shining). It can also be hilarious (Forgetting Sarah Marshall), depressing (Requiem for a Dream), politically-charged (Salò), gratuitous (Showgirls), painful (Blue Velvet), or just plain strange (Antichrist).
Regardless of its origins, naturism has a unique ability to generate a response—be it outrage or otherwise—when viewed through a director’s lens. The best uses of birthday suits in film history go more than skin deep. For nakedness that will stir your mind as much as your loins, check out The 25 Most Important Full Frontal Nude Scenes In Movies.