The Princess Bride
I like Buttercup’s response Westley’s “I told you I would always come for you. Why didn’t you wait for me?”
“Well… you were dead.” The matter-of-fact, yet slightly confused tone is perfect.
Definitely a great moment, but I think I would choose their first confrontation in the film, in which Doc utters my favorite line: “I’ve got two guns; one for each of ya.”
I’ve always loved McKellen’s delivery of the line:
“I will bring you hope, old friend, and I ask only one thing in return - don’t get in my way.”
So chilling, and yet you can feel the old but strained friendship.
Or, we could just do a Darth Vader’s Greatest Hits[sup]TM[/sup]:
“I find your lack of faith disturbing.”
“Apology accepted, Captain Needa.”
“If this is a consular ship, where is the ambassador?”
Hmm…all of my quotes coincided with someone getting choked or Force-choked. Maybe it isn’t what you say, nor how you say it, but whether or not your listener can breathe at the moment. 
This movie is so chock full of them, you can list the whole damn script and be right on.
“Are you hurt?”
“Hurt? You’re alive! If you want I can fly.”
From a fledgling actress, no less… Emma Watson in the first Harry Potter flick, on meeting Ron Weasley: a split-second look up and down, and a very British “Charmed,” that indicates flawlessly but subtly she was anything but.
Not a movie, but a TV series – so sue me 
In the most recent episode of Deadwood, Ian McShane says to Trixie the Whorewho he came close to killing once and generally abused many times but that was when he was irredeemable, after she tried but failed to kill a bad guy for the good of the camp:
You loopy fing c****, with so much affection and love that you’d think you were watching An Affair to Remember.
Alec Baldwin “I *am * God”
I was always partial to “YOU’RE GODDAMN RIGHT I DID!”
The court room goes silent, and Tom Cruise does a great job of looking surprised while also restraining his glee. He collects himself and then orders Jack to be arrested.
From Unforgiven
“I’ll see you in hell, William Munny.”
“Yeah”
With that one word, Eastwood’s character has stopped running from his past, and has accepted that he is a “bad” man. He has stopped blaming his past on the alchohol, and stopped kidding himself that he has changed. He has also realized and accepted all the consequences of that.
Cliff Secord has just had his first big flight using the rocketpack; after a series of misadventures, it ends ignominiously as he skitters across a lake and ends up lying in the mud in a clump of cattails. His friend Peevy finds him: “Cliff! Cliff! You all right?”
Cliff takes off the helmet and draws a shakey breath: “I…like it!!!”
Ellen Ripley’s (Aliens) incredulous “They can bill me!” when told that the alien infested colony she wants to nuke has “a substantial dollar value” attached to it.
And a spoiler tag on the extreme off chance that anyone ever actually watches the animated The Plague Dogs without reading the novel first:
[spoiler]The two dogs, Rowf and Snitter are being chased by the military trying to destroy them and are cornered on a beach. In order to convince Rowf to swim for it, Snitter tells him of an island paradise out in the distance. They both strike out into the water and swim out to sea until eventually they begin to tire and flounder. Rowf says that they must be close to the island by now to which Snitter flatly replies:
“There is no island, Rowf”.[/spoiler]
Just typing it chokes me up. 
Gert Frobe’s genial dismissal to Sean Connory in Goldfinger.
“Do you expect me to talk?”
“No, Mr. Bond. I expect you to die.”
Tony Curtis, proving that every actor has one great line in them.
“I’m Spartacus!”
Harrison Ford to Carrie Fisher, The Empire Strikes Back.
“I love you.”
“I know.”
From O’ Brother, Where Art Thou
Everett: “Well, ain’t this place a geographical oddity. Two weeks from everywhere.”
“Well, nobody’s perfect” - Joe E. Brown in Some Like It Hot
“FUCK YOU - that’s my name” - Alec Baldwin in Glengarry Geln Ross
and a small moment from a sadly negelcted film - Eli Wallach’s “This is the hero who put Joe Zasa in his grave” from Godfather III. So marvellously oleagenous.
mm
A few of my all time favorites:
Vir talking to Mr. Morden:
“Someday, someone is going to put your head on top of a pike as a reminder that some favors come with too high a price. and I will look up into your dead eyes and wave like this” [makes little finger waving gesture].
The next season Londo tells Vir that there is a present for him out in the garden.
It is of course Mordens head on a pike. He waves at the head and flounces off.
Anthony Soprano Jr seems to have a couple beautiful hits in the series:
“Dad, is that what a crack ho looks like?”
“So what? No Fuckin Ziti?”
Moonstruck has a couple of my wife Cyn’s favorites
“Feed another bite of my food to that dog old man and I will kick you till you’re dead”
and
“Someday you’ll be dead, and I will come to your funeral in a red dress”
Prizzis honor,when Turners character tells Charlie she has been doin 3 or 4 hits a year. He says that many.
She says thats not so many when you consider the size of the male population.
Continuing the gangster theme, Gabriel Byrne at the climax of Miller’s Crossing:
“What heart?”
And then he shoots.
In “Downfall”, there’s a scene where Weiderlein (the one of the last German Generals left standing in Berlin) is reporting to Hitler on the hoplessness of the situation, telling him that 15,000 - 20,000 young officers have been killed in the battle so far. Hitler (Bruno Ganz in an amazing performance) simply looks at him with a look of patronising, weary disdain and says
“that’s what young men are for”
in such a fashion that immediatley reaffirms Hitler as the universal gold standard for crazy/evil.
Aliens, during the climax when Ripley is driving the loader and is about to confront the monster, which is itself about to attack Newt:
Get away from her, you bitch!
Tombstone, when Cowboy Bill has just killed the sheriff and Wyatt has him in custody, Ike is threatening Wyatt, who puts his gun to Ike’s forehead.
You’re friends might get me, but not before I turn your head into a canoe.