Not really obscure, but some faves are:
Mage Knight the Boardgame: the ultimate "adventure boardgame" as far im concerned. deep mechanics (there are very few "obvious" decisions in this game) + well realized theme. there are pvp variants, but coop/solo is where it's at. not for ppl who dont like complex rules and long game sessions tho.
Eldritch Horror: aka arkham horror without all the bullshit and w/ some vaguely pandemic-esque "threat management" mechanics thrown in.
Robinson Crusoe: Adventure on the Cursed Island another complex/long game. not really about robinson crusoe, just a generic island survival theme, which is very nicely realized. a sort of middle ground between "euro" and "thematic" games in a way. uses worker placement mechanics but plays rather differently from normal worker placement gams.
Red November: the inspiration for FTL's ship battles (
as per the devs). you and your buddies play a bunch of drunk gnomes trying to pilot a rickety submarine. usues threat management mechanics and simulates both drunkenness and the flow of water. this is a bruno faidutti game, so expect randomness & chaos. it's not a total slot machine tho and is consistently winnable as far as i know.
Reiner Knizia's Lord of the Rings: game that started the co-op trend. some ppl claim this game hasn't "aged well" or is too abstract, i say fuck em. this is a good attempt at a "thematic euro" and while moving white cones across progress tracks might not be the thing ppl intuitively associate with lord of the rings, it makes a lot of thematic sense once you actually play the game.
Ghost Stories: another "threat management" type game. hard & brutal as piss (as in you can die very quickly if you fuck up). dice rolls can occasionally screw you over.
here's some card games too
Space Hulk Death Angel: this one is seriously underrated imo. manages to pack a lot of the original boardgame's "death around every corner" tension into a fast moving co-op card game. randomness exists and
can screw you up but is usually manageable.
Hanabi: same designer as ghost stories. the only co-op game i know that isn't playable solo. very quick & easy to understand so playable with non-nerds, which is a plus.