Xenogears and Chrono Trigger soundtracks, a lot of that is how they evoke good memories of playing the games long ago.
Gaming
I regularly listen to the Subnautica OST while working.
Ori and the Blind Forest
The Xenoblade series has such great OSTs in general. If I have to pick just one track it's probably Engage the Enemy
The Marble Gallery theme from SotN is aboslutely burned into my mind still.
silent hill and no more heroes are both franchises with amazing soundtracks.
Favorite instrumental soundtrack themes are from the early Silent Hill games. The theme from SH1 and the Theme of Laura from SH2 are classics.
Favorite lyrical songs used within the game for plot: Alan Wake has characters in it who are 70s rock gods called Old Gods of Asgard, and the creators got a group named Poets of the Fall to actually write the two songs that were featured from the game and they are actually really great songs. Poet and the Muse is a plot point and Children of the Elder God is played during a really good sequence.