The soundtrack to Homeworld still gives me the willies when I listen to it. It makes the hairs on the back of my neck stand up. (My wife would call it "going pilo", because she’s an animal-geek like that.) Not bad for a 7-year-old game.
Paul Ruskay + Samuel Barber = Awesomely Creepy
My absolute favorite memory of that game is the intro to the seventh mission in the Garden of Kadesh. The voice work, with the halting and flat tones, was perfect. Creepy!