There can't be THE most famous moment, because there are so many movie classics, but here are some off the top of my head:

Raiders of the Lost Ark: Indiana Jones swaps out the idol for a bag of sand, and then gets chased by a huge boulder.

Gone With the Wind: Although most on this board probably haven't seen the movie, it's still regarded as a true masterpiece. The first swear in a movie when Rhett Butler says to Scarlett O'Hara: "Frankly my dear, I don't give a damn," and the scene where he kisses her for the first time.

The Wizard of Oz: "Todo, we're not in Kansas anymore."

Jurrassic Park: The scene at the end where the T-Rex saves all the characters from the Velocaraptors, and then makes his battle cry as a banner which reads, "They ruled the Earth" flies down in front of him.

Star Wars: "I am your father."

Saving Private Ryan: It's still relatively new, but I think everybody can agree the D-Day scene will probably never be re-created as memorably as Spielberg made it.

Psycho: The shower scene.

Forrest Gump: "Life is like a box of chocolates, you never know what you're gonna get."

Now I'll list just a few that probably aren't regarded by many as great moments:

Schindler's List: The entire movie.

Full Metal Jacket: The opening Marine boot camp scene.

Sling Blade:
Doyle: "What are you doing with that lawnmower blade?"
Karl: "I reckon I aim to kill you with it."

what was that from?

The first time Buford T. Justice and the Bandit meet, at least it is my favorite.

Jaws

This scene has been in countless movies, many of them kinda of making fun of it..

...but it's when Clint Eastwood jumps in front of the President right as the guy with his hand-made gun under the paper napkin fires it at him.

The one scottish dude who got hit in the bare ass with an arrow during the first battle from Braveheart.

"Allllllllllllrighty then!!!!" - Jim Carrey "Ace Ventura: When Nature Calls"

Everyone knows that. There are a few other lines from that movie as well.

Rick: Last night we said a great many things. You said I was to do the thinking for both of us. Well, I've done a lot of it since then, and it all adds up to one thing: you're getting on that plane with Victor where you belong.

Ilsa: But, Richard, no, I... I...

Rick: Now, you've got to listen to me! You have any idea what you'd have to look forward to if you stayed here? Nine chances out of ten, we'd both wind up in a concentration camp. Isn't that true, Louie?
Captain Renault: I'm afraid Major Strasser would insist.

Ilsa: You're saying this only to make me go.

Rick: I'm saying it because it's true. Inside of us, we both know you belong with Victor. You're part of his work, the thing that keeps him going. If that plane leaves the ground and you're not with him, you'll regret it. Maybe not today. Maybe not tomorrow, but soon and for the rest of your life.

Ilsa: But what about us?

Rick: We'll always have Paris. We didn't have, we, we lost it until you came to Casablanca. We got it back last night.

Ilsa: When I said I would never leave you.

Rick: And you never will. But I've got a job to do, too. Where I'm going, you can't follow. What I've got to do, you can't be any part of. Ilsa, I'm no good at being noble, but it doesn't take much to see that the problems of three little people don't amount to a hill of beans in this crazy world. Someday you'll understand that. Now, now... Here's looking at you kid.

[img]http://www.openair.co.nz/images/casablanca.jpg[/img]

Casablanca

"I know kung fu" - Matrix
When Patton calls one of his tropps a coward and slaps him.

When the blonde chick is singing "I sing to the sounds...to the sounds of muuuuusiiiic" and walking over beautiful green hills.

"The hills are alive with the sound of music"

I feel really gay for knowing that.

..and the "blonde chick" is Julie Andrews. rolleyes:

casablanca

[img]http://www.filmsite.org/pictures/casa.jpg[/img]

[img]http://utopia.duth.gr/~adamand/destruction/cinema/Apocalypse_Now-02.jpg[/img]

"The horror..."

Platoon: Willem Dafoe kneeling down reaching to the heavens after being shot by Berenger....The whole freaking score to that movie was memorable.

Back To The Future: 1.21 jiggawatts

Dumb & Dumber: Kick His Ass Sea Bass!

American Pie: The pie scene. "MILF."

Die Hard: Yippie Ki yay mutherfucker.

lol !