Wow. Good topic. And some great movie scenes already mentioned.
Ivan Seeking, I must agree that Metropolis gave us some great scenes. The transformation from robot to human women was great, early special effects that I think are still very cool.
Recon, I also like the LOTR movies, but in terms of great scenes, I think the very best thing about them is the remarkable scenery of New Zealand. The place looks beautiful.
Monique, I have never seen Amelie, but I will hire it and have a look.
Njorl, I liked O'Toole in Lawrence Of Arabia, particularly the famous "No prisoners!" Again, lots of groovy scenery in that movie.
Zero, the scene with Luke and Darth Vader is a classic, hero confronting the villain.
Mentat, I have to agree that Equilibrium has given us some great action. I particularly liked the bit where the hero killed all the cops out in the slums. And of course the moment when his feedback to the polygraph flatlined, and the tester realizes why. Nightcrawler taking out the SS was very cool.
Andy, although I dislike the glorification of criminal scum by Hollywood, that scene from Reservoir Dogs was indeed quite cool.
Integral, Indy shooting the swordsman was great. The Blues Brothers has a million great scenes.
As for my own favourites not yet mentioned...
There is a SHORT chunk of computer graphics in Independence Day which I think is great. Two Hornets race down toward the ground and the camera with alien fighters behind, shooting. The city is all rubble and flames. The shot lasts about a second.
Casablanca has so many great scenes that I won't waste bandwidth describing them all. The Maltese Falcon as well.
In Star Wars, when C3PO and R2D2 are wandering around the desert, and C3PO has a hissy fit at R2D2, and they head different directions.
A Knight's Tale, when the hero refuses to run despite certain DOOM! "Doom" should always be said in a big way. :P
Dude, Where's My Car? When Chester says "I've always wondered what a fridge full of chocolate pudding would look like."
Dune, when Paul takes the water of life and does a bit of that space-foldy stuff. (Yes, I know it is not like the book, but I still like the movie.)
Big Trouble In Little China, when Jack Burton is in his truck and says "... And take his advice on a dark and stormy night when the lightnin's crashin' and the thunder's roarin' and the rain's comin' down in sheets thick as led... Just remember what old Jack Burton does when the Earth quakes and the poison arrows fall from the sky and the pillars of heaven shake... Yeah, Jack Burton just looks that big old storm right square in the eye and he says
'Gimme your best shot, pal. I can take it.'"
http://www.wingkong.net