I bought that game, tried to play it for 15 minutes then gave up.
It might be slightly obscure but Heart of Darkness was awesome. It's not very long but it is full of beautiful hand drawn pixel animation and unique elements, a lot of it is only used on a single screen and that made the game take forever to come out. It was Eric Chahi's next game after Another World and the development was truly cursed, it had a ~6 year development time starting in the early 90's which is bonkers.
Gif, spoiler for size
It is well worth playing. There's a PS1 version that's probably a hundred times easier to get running than the PC one but I have never played it.
I played that on PSX. It was murderously difficult. A trial and error fest, clearly grounded in the design of the NES era, but if I remember correctly it came at a time where platformers were significantly easier due to Super Mario 64 and Crash Bandicoot already existing. One of the most unpleasant gaming experiences I've ever had. Didn't help that almost all of the death animations were brutal, too:
That said, I do appreciate the artistry that went in it, and the violence, even though it had that cartoony slapstick element to some of it, looked very visceral and real. This sort of gore and representation is lost in media nowadays, as most of it is just mocapped actors clearly performing some supposedly maiming actions at each other. Sometimes with the receiving part straight up allowing the other to maim them. Heart of Darkness had a very real futile struggle element to it that really made it feel as if the character fought, lost, and got his neck snapped for his trouble. That said, I wonder how many parents got this innocent enough looking game about rescuing your lost dog with an 8+ age rating only to traumatize the crap out of their children.
It also marked the point where I became the big brother who was hardcore into games and could clear parts that most normies would give up on, as none of my family or friends at the time could beat the damn thing. Still, they'd have to put a gun to my head to make me replay that shit. Hate it to this day.
As for obscure games, I've been going through some PSP titles. I've recently no death cleared Obscure: The Aftermath, PSP version. Works very well. No failure runned Gangs of London, which was psychotic on my end, but it did make me gain an appreciation for how smartly designed the controls were for handheld. Gangs of London has controls and shooting mechanics that, while restrictive, work perfectly with the shortcomings of only having one stick. I'd go as far as to say it works slightly better than Vice City Stories and it's overambitious control scheme and expectations. It's an offshoot of the slightly less obscure The Getaway, which still gets spiritual succesors to this day. It was alright, I guess.
Also played The Con and The Hustle, The Hustle being far more obscure as it's a shitty pool game with a frankly psychotic amount of detail and pool aficionado lore, with controls that barely work. Con's really good, a fighting game made also for PSP with very simplistic controls that make you feel at ease with your character at all times. It's not that more traditional fighters work poorly on PSP, Tekken 6 and 5

R are great unless your character is execution heavy, but I found Street Fighter Alpha 3: Max was a terrible fit for how the Dpad felt. Doing rekkas on that will murder your fingertips and blister them to hell. Smash Court Tennis 3 is king of PSP, a tennis game with insanely tight controls, very manageable speed, and an addictive gameplay loop that was perfect for portable and to this day still is great to play if you're just lounging on the couch for a while and got some time to kill.
As for the most obscure shit I've ever played, I think Shaolin, Vs, Slap Happy Rythm Busters and Fighters Impact are gonna be hard to top. Shaolin's legitimately good, Fighters Impact is asscheeks, the reskin Vs is pretty good, capturing that 90's streetwise feel of Tony Hawk or Crazy Taxi and putting it into a fighting game, with a modest but pretty banging soundtrack on the punk rock side and so cringe it's funny on the dark industrial side, and Slap Happy Rythm Busters is just budget Mahvel, Baby. Not terrible Mahvel but just kinda uninspired.
Generally great, memorable character designs, and the Mia character, reused from Vs. was something of a dark horse in the 90's amongst fighting gamers for being a very toned chick showing her washboard abs and a high rise thong. As ubiquitous as cheesecake was back then, Mia always stood out just for being so creative in that she was affiliated with a street gang, with the presumable blackjack, drugs and hookers implications, and the first, and pretty much only with a heavy focus on her midriff and hips rather than T n' A. Best damn character in the game, too. Supposedly she was a DJ but her gang had a literal "Businessman" in a Huggy Bear suit with a wide brim hat who did karate, so... Yeah. She got an otherwise mediocre game in a post Tekken 2 era on many magazine covers just on her attractiveness alone. Really shrewd marketing tactics.
Oh, and of course, Britney's Dance Beat on the PS2, a terrible dancing battle game that was often in the discount bin for as low as 5 bucks. I still felt ripped off, but y'know, I thought maybe it was like bemani. It... Really wasn't. In fact, I'd say the fucking beats were off, since to this day I can't get perfect songs and I could SWEAR I was nailing that timing. Coming from the very easy, very satisfying Bust A Groove really did a number on me, I was basically spoiled for any sort of rythm game after that.