120 Days of Sodom (1975)
Also known as Salò, this film is based on the book by Marquis de Sade which he wrote while imprisoned in the Bastille in 1785. Sade was incarcerated in prison and in an insane asylum for nearly half his life.
In Pasolini's film, four men of power in Italy: the Duke, the Bishop, the Magistrate and the President, collect a group of teenagers, and subject them to 120 days of torture. Graphically violent, the film was, and is still, banned in several countries for its depiction of sexual torture - particularly to children, as they are raped, mutilated and forced to eat faeces. Despite all of this - the film still excludes some of the horrors of the book - it's no wonder why the word Sadism was derived from Marquis de Sade's name.