From Gladiator, Joaquin Phoenix mocking Russell Crowe about his dead family-
Commodus: They tell me your son squealed like a girl when they nailed him to the cross. And your wife… moaned like a whore when they ravaged her again and again… and again.
Does anything come close to this one? I remember in the theatre actually laughing out loud in disbelief that this was said. Pretty hardcore.
“In order to understand Death you must fuck Life in the belly”
From “Andy Warhol’s Frankenstein” (which Andy Warhol had virtually nothing to do with). Among other things, it bothered me because the quote seemed backwards – the Doctor wants to understand Life, after all, and he’s violating a corpse.
Your mother was a hamster and your father smelt of elderberries.
Rhett to Scarlett: “Frankly my dear, I don’t give a damn.”
Pretty provocative in it’s day and much more quoted as a put down than just about anything else since then.
I’ll be back! 
Your mother sucks cocks in hell.
As this doesn’t have a factual answer, it seems better suited for Cafe Society. I’ll move it for you.
Thanks and sorry, meant to put it there in the first place.
Yeah, I was gonna say this one.
I haven’t been fucked like that since grade school.
From Welcome to the Dollhouse:
Punk kid threatening young girl- Yo Weiner, you better get ready, ‘cause at three o’ clock today, I’m gonna RAPE you!
From The Way of The Gun after Sara Silverman is being bitchy…Said to her boyfriend:
“You better shut that c*nt’s mouth before I fuck-start her head.”
Not a line from a movie, but a purportedly true story about Paul Lynde: Lynde was a passenger on a red-eye flight from L.A. to NYC (or vice versa), and behind him was a mother holding her baby. The baby cried nonstop for several hours, prompting Lynde to turn around and yell - “Lady, if you don’t shut that baby up, I swear to God I’m going to f**k it!”
Sooner or later, Logo will get around to making a bio-pic about Paul Lynde, and I’ll watch it just to see if they include that very un-P.C. moment.
Linda Fiorentino calling Peter Berg a “farm faggot” in The Last Seduction after his TMI revelation always struck me as an exceedingly low blow. Which I guess was kind of the point.
Originally David Fincher’s script had a different line in place of this one. The line was. “Oh God, I want to have your abortion.” Fox execs begged Fincher to change the line. They hounded him for weeks, saying that anything would be better than that. What you saw in the theater was what David came up with to replace it. Fox execs tried to get him to change it back. He decided that he liked the grade school line better.
“Your mom goes to college.”
I got nothin’.
Morris Day in Purple Rain: “How’s the family?”
Hotel Rwanda
“You’re not even a nigger. You’re an African.”
Damn, I can’t believe someone beat me to this one.
GildedLily that was the one I was going to use but I need to wait till I get home, I wouldn’t dare write that from work. 
Yeah, I was gonna put that line too, but I think the line was:
“You better shut that fucking cunt’s mouth before I fuck a hole in her head and come some sense into her.” It’s particularly poignant because instead of hitting the boyfriend he beats down Sarah. Unfortunately that scene was the only memorable one in the entire movie.