Secret of Mana - especially the Japanese/metallic music when you fight the big boss at the end.

System Shock 2 - the techno music that kicks in when you unlock the door unleashing the first hybrids was too much. First time I encountered it, I had to switch off the game, what with the heart-pounding music and the sheer terror, I needed to escape. Strangely, enough the same thing happened last time I tried to replay it.

Morrowind - had a nice theme. Very short and very often repeated, but somehow I still liked it every time it started up.

Fantasy General - perhaps the only strategy game that was markedly improved by virtue of its music.

Vampire Bloodlines - the dance music in the daughter of Janus's nightclub was excellent. After a traumatic episode, you and your character could lose yourself and regain some humanity by succumbing to it.