Mine is from the TV show Friends, Yes, yes it is…IN PRISON!" (1:10 mark)
The whole setup is perfect and then Ross comes in with a great look on his face the perfect reaction.
Also my favorite that sticks with me from Tombstone is
Turkey Creek Jack Johnson: Why you doin’ this, Doc?
Doc Holliday: Because Wyatt Earp is my friend.
Turkey Creek Jack Johnson: Friend? Hell, I got lots of friends.
Doc Holliday: …I don’t.
John Merrick: There’s something I’ve been meaning to ask you for some time now.
Dr. Frederick Treves: What’s that?
John Merrick: Can you cure me?
Dr. Frederick Treves: No. We can care for you, but we can’t cure you.
John Merrick: [matter-of-factly] No. I thought not.
Both actors superb, but that last line still hits me like a brick.
The one that brings tears to my eyes, even though it’s been at least 15 years since I’ve seen it:
Dr. Frederick Treves: Am I a good man? Or a bad man?
It was the first film my wife and I saw together, both of us crying at the end. Of course, the film is a sort of Voight-Kampt empathy test, and if it doesn’t move you to tears, you just may be a Replicant.
I say that things like this should replace CAPTCHA as the test of humanity.
If you can watch the first 20 minutes of UP without crying…you’re definitely a robot
Good idea, but it would make logging into sites slow.
Damn you, you beat me. 
Agreed, although the last 100 minutes seem like they were written by a robot.
“Much to learn you still have, my young Padawan.”
I love the line because Yoda said it to Christopher Lee (Darth something or other). Damn, Yoda is old.
KINDERGARTEN COP. No, not the line about the tumor; not any of Schwarzenegger’s lines, even. “You’re not so tough without your car, are ya?”
It’s all in the delivery. (Okay, one-third of it is the perfect set-up, but her delivery is two-thirds of it.)
Probably my favorite passage from an eminently quotable movie. Well, that and another line that I occasionally use in my own life:
“That is a hell of a thing to say to me!”
And for sheer perfect enunciation, one of my favorite lines ever:
“What a buncha fuckin’ bullshit.”
– Dennis Farina, Get Shorty
“I *was *first in line. Until the little hairball was born.” – Jeremy Irons as Scar in The Lion King.
Every line he has in that movie is great, but there’s something about Irons’ petulant, threatening tone that really gets across Scar’s menace.
Vilkomen! Bienvenue! Welcome! C’mon in!
I’ll see your “I don’t care” from *The Fugitive *and raise you two words from Men in Black:
Will Smith walks in as Tommy Lee Jones is watching his long-lost love via computer. Tommy Lee hastily clears the screen in embarrassment. Smith natters on about how it’s better to have loved and lost than never to have loved at all. Tommy Lee freezes him with a stare and says “Try it.”
The amount of loss and frustration and world-weariness he packs into two words is amazing.
“Don’t 'Sir” me, young man, you have no idea who you’re dealing with"
I can do a pretty spot-on Sean Connery impression. Frequently, when I’m asked if we’ll meet our quarterly numbers, I will inflect my best Scottish brogue and announce:
“Pershonally, I give ush one chanshe in three (Personally, I give us one chance in three).” - Sean Connery, Hunt for Red October
“Please, dad.”
“You ain’t no Presidential appointee, Elliott. The one that hired you was me. You got thirty days.”
Wilford Brimley in Absence of Malice.