Roy Batty's death soliloquy. Quite possibly the CMoA for Rutger Hauer as an actor, too, considering that he ad-libbed it.
It's so good, it bears quoting:
I've seen things you people wouldn't believe. Attack ships on fire off the shoulder of Orion. I watched C-beams glitter in the dark near the Tannhauser gate. All those moments will be lost in time, like tears in rain. Time to die.
The entire ending sequence, where Roy is chasing Deckard through that creepy building, lights flashing, and the freaky sounds and dialogue on Roy's part. Then the climax up on the roof, even Deckard was reduced to trembling. That scene embodies a CMoA.
Most of the soundtrack by Vangelis. It is an excellent example of how to use electronica intelligently. Above all of these, however, is the main theme of the movie, played over the ending credits.
The contrast between the various "official" versions and the famous "workprint" version of the scene where Rachael watches Deckard try to clean himself up after almost getting beaten to death is a great illustration of how music works in movies:
In the workprint, creepy dissonant noise music highlights that Deckard is vulnerable and Rachael could easily kill him at that point if she decided it was her best chance at survival and freedom.
In the later "normal" cuts, romantic music implies Rachael feels sorry for Deckard and protective of him. The entire meaning of the scene is completely different, even though nothing changed except the music.