Giorgio Moroder vs. J.S. Bach, The Duel. This cello + synthesizer duet is one of my many favorite bits from this movie, and from what I've seen, that seems to be a common reaction.
Giorgio Moroder, Madeline's Theme. Video, Let It Run, and The Duel make me nearly giddy every time I hear them. This one puts me in a melancholy yet hopeful mood that's kind of hard to describe. Give it a listen. (And see the juxtaposition of Virginia Madsen slowly starting to cry, and a computer's motherboard treated as landscape by the cinematographer, all of which makes perfect sense in context.)
Feudalism: Serf & Turf