Wow. I concur with a LOT of these suggestions, especially from Raiders, The Terminator, and Blade Runner (I, too, love Rutger Hauer's end speech; I also love the dialogue in Tyrell's death scene: "Nothing the god of biomechanics wouldn't let you into heaven for."). It doesn't seem like many comedies have been mentioned yet, though, so I'll add...
Spaceballs
"Whatsa matter Colonel Sanders? CHICKEN?!"
"We ain't found shit!"
"Oh no! Not again!"
"Funny. She doesn't look Druish."
"Druish princesses are often attracted to money and power, and I have both, and you KNOW it." (That brilliant scene was improvised by Rick Moranis according to Mel Brooks's commentary on the DVD.)
Ghostbusters
"I think we should split up." "Good idea." "Yeah, we can do more damage that way."
"Listen. Do you smell somethin'?"
"It's the Sta-Puft Marshmallow Man."
"Ray... When someone asks you if you're a god, you say YES!"
"That would've worked if you hadn't stopped me."
"You want this body?" "Is this a trick question?"
"Nice doggie. Cute little pooch. Maybe I got a milkbone..."
"Okay... so... she's a dog."
"Yes, it's true. This man has no dick."
"Egon, your mucous."
And a few other non-comedies:
Indiana Jones and the Temple of Doom
Okay, this is a weaker entry in the Indy series, but still pretty good, IMO. And for me, it's worth the whole price of entry just to see Harrison Ford look at his predicament on the bridge and say, "Oh, shit." I swear, Ford is the master of perfect delivery.
The Abyss (Special Edition)
The whole end sequence with the tidal waves. The end of the theatrical version isn't even remotely as powerful. "How do you know they're really going to do it?"
Airplane 2: The Sequel
Here's a movie that doesn't belong on anybody's top-ten list, but since we're talking about individual scenes (and someone else quite rightly already mentioned that pretty much all of the original Airplane! qualifies), I'll mention a scene in the second one that gets me every time: Robert Hays opening the door that says "DANGER: VACUUM", then getting attacked by a vacuum cleaner hose.
The Changeling
The seance scene. CREEPY, CREEPY, CREEPY! Also the banging of the "pipes" in the middle of the night and the ghost trying to climb up through the floorboards of the little girl's bedroom that was built over the well. I never get tired of watching this movie.
Ferris Bueller's Day Off
"Bueller? Bueller?"
"I asked for a car, I got a computer. How's that for being born under a bad sign?"
"Ferris, my father loves this car more than life itself." "A man with priorities so far out of whack doesn't deserve such a fine automobile."
"I do have a test today. that wasn't bullshit. It's on European socialism. I mean, really, what's the point? I'm not European. I don't plan on being European. So who cares if they're socialists? They could be fascist anarchists. It still doesn't change the fact that I don't own a car."
"Rooney!" (Cameron's fake voice over the phone)
Full Metal Jacket
Well, pretty much the whole first half. I like the entire movie, but the first half is just incredible with the gunnery sergeant.
Pale Rider
The whole end scene where Clint's character goes from "preacher" to ass-kicking gunslinger.
The Shining
"Heeeere's Johnny!"
"Wendy! Darling! Light of my life! I'm not gonna hurt ya. You didn't let me finish my sentence. I SAID... I'm not gonna hurt ya. I'm just gonna bash your brains in. I'm gonna bash 'em right the fuck in."
The elevator doors filled with blood.
... and some other great stuff I'm probably forgetting. I know Stephen King didn't like Kubrick's adaptation, but I think it's still a great film as a Kubrick movie rather than a Stephen King one.
Star Trek II: The Wrath of Khan
Pretty much any scene with Ricardo Montalban, who is wonderfully (and appropriately) over the top in his role.
Star Trek IV: The Voyage Home
Someone else already mentioned this movie, but I'll reiterate how great some of the dialogue is (and the delivery):
"I love Italian. And so do you."
"No ma'am. No dipshit."
"Double dumb-ass on you!"
The Witches of Eastwick
Jack Nicholson's speech in the church: "Do you think God knew what He was doing when He created woman? Huh? No shit. I really wanna know. Or do you think it was another one of His minor mistakes like tidal waves, earthquakes, FLOODS? You think women are like that? (pukes) S'matter? You don't think God makes mistakes? Of course He does. We ALL make mistakes. Of course, when WE make mistakes they call it evil. When GOD makes mistakes, they call it... nature. So whaddya think? Women... a mistake... or DID HE DO IT TO US ON PURPOSE? 'Cause I really want to know! 'Cause if it's a mistake maybe we can DO something about it! Find a cure! Invent a vaccine. Build up our immune systems. (maniacal laughter) You know... twenty push-ups a day, and you NEVER have to be afflicted with women EVER AGAIN!"
The Empire Strikes Back
TONS of great scenes in this one, but we have to note the classic: "No...
I am your father."
Actually, I'll specifically point out one more: Han Solo banging on the controls of the Millennium Falcon to get it to power back up when it starts to die. Hilarious.
Return of the Jedi
The scene where Luke finally loses it and attempts to kill Vader. The choral music in the background is breathtaking, and the emotions of the moment are the culmination of the entire saga.
Conan the Barbarian
Another movie that's already been mentioned, but I'll mention some favorite scenes:
"Steel isn't strong, boy. Flesh is stronger." That whole sequence, really. James Earl Jones is fantastic.
The execution of Conan's mother at the beginning of the film. Basil Poledouris's music, which is AMAZING throughout the film, reaches one its most awe-inspiring moments here.
The finding of the sword in the ancient tomb (and ditto on the music here, too).
The raid on Thulsa Doom's palace.
The final battle, especially with Rexor. ("Do you want to live forever?")
Die Hard
Tons of great stuff, but the standout has to be Bruce Willis's leap off the building with the hose tied around his waist.
Okay, I think I'm tapped out for the moment.
Blake