Thundercrack! (1975) 
Oh my, what did I watch... The story is pretty flimsy and the acting is questionable, but there is something to this film that keeps you hooked. It's like watching an art school experiment, filmed with noir-ish lighting it looks beautiful and the framing of each scene is likened to looking at still photography. However the dialogue is very un-natural and contains more exposition than an episode of Dawson's Creek
Put all of that together with various scenes of masturbation, and hardcore sex between woman and woman, man and man, man and woman, and a gorilla... makes this film unlike anything else I have ever seen, and it will definately put me off eating a peeled cucumber any time soon!