I haven't actually watched this Pasolini movie but I really want to after seeing this clip from its conclusion - it's insane! I'm pretty sure Pasolini himself appears at the very end as the guy closing the book. (Not safe for work.)
UPDATE 7:25 pm: Well, it was nice while it lasted but Youtube took the clip down, not surprising since it involved a demon literally pooping out bishops and friars in close-up.
Courtesy of New York Magazine's Vulture blog about "The Ten Most Anti-Christian Movies of All Time", for this year's War on Christmas I guess.