My all-time favourite film moment is the love scene from Blade Runner, with Harrison Ford and Sean Young. It's about 10 minutes long and within it are all the things I love most about film.
The scene begins in Deckard's apartment. Rachel has just saved Deckard's life. The minimal and awkward exchanges between the two are in perfect harmony with the music and sound design. Waves of sound and light bleach out the frame randomly and fill the spaces in the scene with a rich ambience. Rachel watches Deckard clean himself up whilst Vangelis's music becomes progressively more abstract. This moment has an ambiguity to it that is impossible to describe, but gives me goosebumps every time.
Second to this is the scene in The Elephant Man where John Merrick (John Hurt) has escaped from the circus and the brutal clutches of Bytes (Freddie Jones), and is making his way back to London. On arrival at the station, cloth sacking covering his face, he is harassed by an oik who keeps asking "'ere mister, why is your 'ead so big?" Merrick tries his hardest to evade the rapidly growing posse of nosey people who eventually drive him down into a public toilet. Cornered, his sack is whipped off and the onlookers gasp. At his wit's end John Merrick cries, "I am not an animal!" It is difficult to pick a best scene from The Elephant Man, because in my opinion it is a perfect film. What I remember most about this scene is how desperately I wanted to jump into the TV set and machine-gun down all those people who were busting his balls. I can't watch it too often as it always makes me sob.