The helicopter approaching the alpine meadow where Maria is marching with arms swinging.
Ascot scene (especially those women walking with their umbrellas)
Travis Bickle’s rat-fink dialogue with the tall secret service agent.
Al Capone moving his finger up and down from his ear to the floor: “I want him dead, I want his entire family dead, I want his house burned to the ground.”
Flying bicycles in E.T. The Extra-terrestrial.
Dance to “Moses Supposes” and “Make them laugh”
Linda Blair walking down the stairs like a spider on its back (edited out)
Downey making an impromptu upon his arrival in front of Akroyd in “Chaplin”
Legolass swinging from Gimli’s horse’s neck onto its back behind Gimli
Norton’s dinner table monologue in front of his family and guest Elliot Gould.
Neeson crying like a baby after receiving his gold ring.
Robert Strauss singing “I love you” in “Stalag 17”
Just the sight of Gregory Peck with his whalebone prosthetic on the deck of the Pequod
Samara’s face
The scene at the end of Empire of the Sun where Christian Bale sees his parents and waits for them to see him.
HAL.
I guess it would be part of the final scene in the movie Play It Again, Sam. Woody Allen quotes from Casablanca without mentioning that it’s a quote. Diane Keaton says that he’s said something beautiful. He admits that it’s from Casablanca and he’s waited all his life to say it:
The hallway hammer fight scene from Old Boy.
The fight scene from They Live.
The end of The Man From Earth.
Tilda Swinton’s Karen Crowder getting caught out in the last scene of Michael Clayton.
The helicopter rescue scene from Superman.
The curb-stomping scene and the shower rape scene from American History X.
Kong busting down the big doors.
Some REALLY great scenes here, but no one mentioned Blade Runner?
All those… moments… will be lost in time, like [coughs] tears… in… rain. Time… to die…
*
Wayne in True Grit* is damn good as well.
We need more Youtube up in this thread!
I love the BladeRunner scene!
And I tried to find the silent coach scene from Black Sunday but I didn’t have any luck. 
When Alan Arkin jumps out at a blind Audrey Hepburn from behind the refrigerator door in Wait Until Dark. I still jump every time I see that.
Get away from her, you BITCH!
Do I have to explain this one?
I saw this film in New York and the whole theatre cheered.
William Munny returns to Greeley’s saloon, Unforgiven.
Kikuchiyo rants, The Seven Samurai.
Max and Herman’s escalating revenge cycle, Rushmore.
Most great movies have several memorable scenes so, except for a few obvious cases (e.g. Lauren Bacall teaching Humphrey Bogart how to whistle) it’s hard for me to think of examples of movies with singularly memorable scenes.
I watched Inn of the Sixth Happiness when I was a little kid 55 years ago and remember absolutely nothing about it except the last scene, which therefore must be memorable by definition! One hears “This Old Man, He Played One” sung in the distance: the heroine has successfully brought 100 Chinese children through enemy-controlled mountains, keeping their spirits up with song.
(I just watched the movie again, via YouTube, and don’t really recommend it unless you enjoy tedious and sentimental romance. It is based on a true story, though with some changes: the real-life Gladys Aylward’s hotel was called The Inn of the Eight Happinesses.)
I’ve heard that you’re a low down Yankee liar.
The scene in Vertigo where she’s finally convinced James Stewart that she isn’t Madeline, and he walks off, and then she turns around, the music swells, and it shows that bell tower scene again. Whoa.
Two from Tarantino:
Pulp Fiction, the Mia Wallace getting a shot sequence. Also the dance.
Kill Bill vol. 1, the animated O-Ren Ishii sequence. How else are you going to get away with telling a tale of a child who sees her parents getting killed, then gets her revenge 4 years later (at the age of 11, nonetheless) while she’s having sex with her parents killer other than animating it?
I guess that’s 3, actually.
The Last of the Mohicans - when Alice jumps
Tombstone “I’m your huckleberry” when you know Ringo is totally hooped
For A Few Dollars More - The hat duel
I just thought about this one. Too cool. Not a gunfight, but more a shooting game. The atmosphere is great. It’s at night and for the heart of the sequence there is no dialog.
Reallly brilliant.
Al Pacino’s rant at the school hearing near the end of Scent of a Woman.
Network : You have meddled with the primal forces of nature, Mr. Beal!
Where Ned Beatty explains how the world really works.