I am always looking for new music. I will start with my fav less(er) known game OSTs from my collection in alphabetical order:

- Archibald's Adventures

- Einhander

- Master Rallye

- Project IGI

- SimCity 3000

- Switchball

- Trials Fusion

- Unreal (my absolute fav, arguably well known but only among older PC gamers)

Dunno about obscure, but Noriyuki Asakura was my first love when it comes to game music and doesn't come up enough in these conversations:

I also really wish there was more stuff like this out there:

EDIT: Oh! I do know of an obscure diamond in the rough:

Lunistice

Prodeus

Turbo Overkill

FF6 soundtrack, it's like a ghibli movie

Deracinè. A game I played solely for the music and the vibe of the building they created in the game in VR, pretty shit game otherwise. 

Not sure if its obscure since its from Professor Layton, but this tune might be the most beautiful piece of video game music Ive ever heard

Zone of the enders 1 and 2 had incredible music/fantastic art design and(at least for me) great gameplay.

This is probably the best boss battle theme I ever heard.

I don't know if it's obscure, but Wizards and Warriors intro has always been one of my favorites.

Best relaxing soundtrack and a shame the game is stuck on PS3.