Not sure if either of these count as "obscure" but I like them both & and they haven't been mentioned yet
Exanima is a physics-driven ARPG set in a dark, low fantasy world. It is the test bed for the developers' future game, Sui Generis, which is supposed to be an open-world RPG that would use the same systems as this game.
I will emphasize the "physics-driven" part of the descriptor; nearly all of its game mechanics interact with its physics system in a way similar to games like T.A.B.S or Human Fall Flat, except it's been so ridiculously refined that I have honestly never seen anything like it before. I won't get into the technical weeds, but from what I've read, it is seriously impressive, and I'm pretty sure the programmer working on it has severe autism.
The combat in particular is the main draw right now, and I cannot really think of anything like it on the market. It has the learning curve of an inverted cliff face, but once you get the hang of things it is really satifying to play and can be endlessly mastered by people. I've heard it described as a "martial art", which is probably a fitting description, as I've seen multiple HEMA nerds comment on how many of the sport's fundamental concepts can be applied to the game. If you can tolerate the learning curve and a few online guides, nothing else is like it.
Peglin is a fun little deckbuilding (orb-building?) roguelike, with the main difference being your cards are Orbs, and you deal damage by playing Peggle. The more pegs you hit, the more damage you do.
The orbs act as modifiers that can affect the damage per peg, the peg's physics, what enemies the orb targets, etc.
Its a simple concept executed very well, with a surprising amount of variety when it comes to the orbs. I actually enjoy the added skill check that comes from trying to maximize the amount of pegs hit compared to just using a card, and in the moments where you're up against a very strong enemy with an underpowered deck, it makes things feel a little more in your control.
If you need an engaging time killer, check it out.
