Like many have said, the Legend of Zelda scoring, are amazing. I haven't encountered one yet that I didn't love. The GTA series radio soundtracks, and the Bethesda Fallout radio soundtracks were really cool. They really widened my appreciation for styles of music I would never have listened to otherwise. I don't think I would have ever learned an appreciation for 1940's pop music otherwise
Dark Souls is in a realm of its own. Kind of like Zelda, its very poignant.
The credits of Driver 2 completly blindsided me with "just dropped in".
https://youtu.be/Naf-wVHUCcc?t=1m50sI think the absolute coolest moment I've ever experienced in game scoring/soundtrack is in Hitman 3 when you walk into a bar in the Rendezvous in Rotterdam, and Immortal by Clutch is playing in the bikers "den".