I'm not going to talk too much about Salo, a 1975 film by Pier Paolo Pasolini that I saw the other night... other than to say it was the single most disturbing film I've ever seen in my life. I've seen obscure gorefests in the sake of gross-out, but this was on another level. Pasolini is one of the master craftsmen of cinema and to put him on such a project makes this film transcend how disturbing this is. So well made and acted, it is like a piece of priceless art covered in shit (literally).
Even now, I'm unnerved by the film. The acts committed and the basic story of the film is so outrageous yet ground in reality, it makes you question humanity in a way that I never have before (even more so than Schindler's List).
I will leave you with the production description on Amazon:
A loose adaptation of the Marquis de Sade's The 120 Days of Sodom, Pier Paolo Pasolini's Salò is perhaps the most disturbing and disgusting films ever made. It is also one of the most important, offering a blistering critique of fascism and idealism that suggests moral redemption may be nothing but a myth. Criterion presents Salò in its uncut, uncensored version.