I decided to put some serious thought into this and decided to go in another direction and talk about some moves that I know exist, but never actually end up using for some reason or another. Technically these aren't obscure but I doubt people really think about them often.
#1: Mud-Slap. A 20 base power Ground move that lowers accuracy, basically the Nuzzle version of Sand-Attack. A lot of pokemon actually learn this move compared to Sand-Attack, but in practice Sand-Attack is on a lot of early-game mons where it's most useful, while Mud-Slap is most widely distributed through postgame move tutors in Gen 3 and 4. For some reason this is a special move, but it's so weak it doesn't even matter. It also has a low 10 PP which is the same as Earthquake. This move is never really a viable choice over just attacking and killing things.
#2: Fury Cutter. This move gets stronger as you use it more times in a row, capping out at 160 power. Unfortunately you can usually just use a different move to achieve the same results,
though the multiplier effect can be effective in niche earlygame situations. Originally this move only had 10 base power and was buffed twice over the generations to actually be usable. Interestingly enough, in
Gen 2's development days, originally Fury Cutter would cap out at 255 BP, then nerfed to 5 boosts at 240 (with 15 BP as a base), then nerfed down to the 10 BP of vanilla Gen 2. There's a similar concept in Rollout, but Rollout has the better Rock-typing and doesn't cap out, even being buffed by Defense Curl. Also, Rollout has a much scarier reputation thanks to Whitney's Miltank. I think it's more that the AI is locked into the move and can't mess up, while the AI probably doesn't even know how to use Fury Cutter properly. Even the Metronome item exists as a weaker effect, but you can use with on a good move instead.
#3: Attract. Now everyone probably knows about the word Attract and almost every Pokemon learns this by TM, but ironically I would bet almost nobody has seriously kept this move ingame or competitively. On the plus side it's a 50% action blocker that never wears off, but why use a moveslot on a niche move that you can't plan around when you can just attack instead? It gets worse in competitive where there are more genderless legendaries around, and on a related note the most attention it ever gets is memes about genderless pokemon learning it. Even gamefreak has moved on from trying to make Attract a thing, with specific infatuation interactions like Oblivious and Destiny Knot being reworked into other mechanics instead. Even every mon with Cute Charm has a much better ability to use.
#4: ViceGrip/Vice Grip/Vise Grip. This is a generic normal type move that is probably most known for getting its name changed 3 times and I don't think I have ever seen it ingame.
#5: DynamicPunch. This move isn't technically obscure, but has lost its individual identity in my opinion. Nobody remembers DynamicPunch as a 50% accurate fighting move that a lot of pokemon learn, because the majority of its 150~ potential users don't care about this move and I don't even know who any of them are. When I think of DynamicPunch I think more of its (ab)users like No Guard Machamp or even Golurk, when it's not even a signature move. There are clones with lesser distibution like Zap Cannon and Inferno, but it's a bit sad that DynamicPunch is only known today because they had to make an ability in Gen 4 to make it usable with on one pokemon.
#6: Iron Tail. This is a pretty bad move all around, being from Gen 2 where all steel moves were named after a steel synonym and body part. 100 base power is okay, but 75% accuracy really hurts its damage output and being Steel-type does it no favours. Not even that many Steel-types learn the move, so it's just bad coverage, and apparently Pikachu has it in the anime. Do not use this move.
#7: Icy Wind. Again this is another move that there just is no point to using practically. 55 power with 95% accuracy and only a Speed debuff to make up for being worse than Aurora Beam. This move is just very weak and you probably have access to much better Ice-type moves if you even learn this, and if not it's so weak it's not even worth the coverage.
#8: DragonBreath. This move is actually pretty okay, but is stuck in the role of an earlygame Dragon-type move. In competitive you'll usually be using the strongest moves like Dragon Pulse or Outrage, while ingame you probably won't even have a dragon early enough to use this with, and it's just not that good coverage-wise or accessibility-wise.