Aw, silenus beat me to it. I laughed my ass off at that movie.
Esp funny was The Banana Splits theme song being played during one of Hit Girl’s rampages. I heard complaints about it though - “what’s with the corny cheese song being played during the fight scene?!”
I tried to tell them, “but it was the banana splits! Playing that song made that scene extra hilarious!”
But much of the movie’s audience was/is too young to remember who The Banana Splits were - let alone any theme song. 
I loved the use of pinyan Chinese in the ‘Serenity’ movie <and of course, in the series that spawned it>. Always fun to have a dictionary on hand so you can tell just WHAT they’re saying, like this one… http://fireflychinese.kevinsullivansite.net/
I just enjoyed filling in the blanks. 
User name reflects my bias, and no disrespect to the great R. Lee Ermey, but the greatest swearing is below (cribbed, of course, from the first movie):
So endeth the lesson.
“You fuck my wife?” from Raging Bull.
“How shall we f*ck off, oh lord?”
“Did you order the code red?”
“YOU’RE GODDAMNED RIGHT I DID!”
Goodfellas for menacing swearing.
You mean, let me understand this cause, ya know maybe it’s me, I’m a little fucked up maybe, but I’m funny how, I mean funny like I’m a clown, I amuse you? I make you laugh, I’m here to fuckin’ amuse you? What do you mean funny, funny how? How am I funny?
Sometimes it’s not about vulgarity, as much as it is lack of class that wins the damn thread (with thanks to the OP for reminding me about it)
And Ken and Harry arguing in In Bruges. You just have to love why Harry is offended.
Ken: Harry, let’s face it. And I’m not being funny. I mean no disrespect, but you’re a cunt. You’re a cunt now, and you’ve always been a cunt. And the only thing that’s going to change is that you’re going to be an even bigger cunt. Maybe have some more cunt kids.
Harry: [furious] Leave my kids fucking out of it! What have they done? You fucking retract that bit about my cunt fucking kids!
Ken: I retract that bit about your cunt fucking kids.
Harry: Insult my fucking kids? That’s going overboard, mate!
Ken: I retracted it, didn’t I?
Not a movie, but this is a great scene from HBO’s The Wire. (Homicide detectives investigating a murder.)
Well if we’re going to expand to TV series, then any fucking 2 minute stretch of Deadwood will kick any of these cocksuckers’ cunt smelling asses any motherfucking day of the cocksucking week.
But that is a pretty cool scene from The Wire.
Chevy Chase from the OP
IMHO what a pitiful use of profanity, not funny at all. must be a Y chromosome thing.
What Tangent said
Sometimes you just gotta say “What the fuck.” (Risky Business)
Yippee-ki-yay, motherfucker. (John McClane - Die Hard)
one of my best friends, since passed, used to say, “just put it in your fuck it file”
best advice i’ve ever gotten
You win. I read that Ermey’s boot camp scenes were some of the very few times that Kubrick would let an actor improv.
A close second.
“Wu, say ‘cocksucker.’”
I forgot about this one, Betty White in Lake Placid. Here’s some excerpts:
Sheriff Hank Keough: Ma’am, your husband Bernie, you didn’t by any chance lead him to the lake blindfolded?
Mrs. Bickerman: If I had a dick, this is where I’d tell you to suck it!
Mrs. Bickerman: Murders and rapes in the city, people bomb planes, can the police stop 'em? No! But feed one little cow to a crocodile…
Sheriff Hank Keough: You’re gonna stay right here until the police show. You’re under full house arrest.
Mrs. Bickerman: Thank you, officer fuck-meat!
Mrs. Bickerman: You can’t take a cow by eminent domain!
Sheriff Hank Keough: We just did.
Jack Wells: We won’t let her get hurt, Ma’am.
Mrs. Bickerman: You’re all cocksuckers! I knew it first, I just didn’t want to say it!
I like the(often forgotten) story Pesci’s character tells that makes Liotta’s character say “you’re a funny guy”.
Falling Down, 1993
**Reporter: **What cooperation was there between Pacific Division and Downtown?
**Captain Yardley: **Not to denigrate the Venice Police, but it was one of our fellows that put this together.
Yardley sees Sgt Prendergast, played by Robert Duvall.
**Captain Yardley: **Prendergast!
**Captain Yardley (to reporters): **This is Sergeant Prendergast. Damn fine work, Prendergast.
Prendergast: Fuck you, Captain Yardley. Fuck you very much.
**Reporters: **I can’t believe-- Did he just say that?
**Captain Yardley: ** You’ re welcome.