I Am Bread because you play as a slice of bread. What's not to love?

Also Pony Island because it has 10 million gamer jokes.

Also also Hatoful Boyfriend because you get romantically involved with pigeon students.

Vib Ribbon.

Rhythm game with very basic graphics. Controls were tight, and the K-pop music was addictive. You could also insert your own music CD to the PS1 to create your own levels which was pretty mind-blowing at the time.

Most of these I'd never even heard of; great stuff, keep 'em coming!

For moi, Project Zero 2 Wii Edition comes to mind; a re-imagining of a PS2 era J-Horror title that arriving very late in the Wii's life, was never released in North America, and only sold like 10,000 copies lifetime in PAL Land.

It's a superb slow-burn of atmospheric horror, with a wonderfully moody sense of creeping dread and the same ingenius "touch" mechanic as the infamous Japan-only Fatal Frame 4, where you have to hold A to slowly reach out to an item or a doornob or look under a bed, testing your nerve as you have to be ready to let go in an instant if something attacks you. Fantastic stuff, highly recommend it if you enjoy the PS2 era of horror games like Silent Hill 2/3.

Yeah, it's awesome! We had to stop playing it every now and then because we were too afraid to keep going. Excellent atmosphere!

At first it may seem like a generic race kart game like we had so many on PS1 and if you look to reviews scores it seems bad but I loved it.

It came with plenty of content 25 characters/kart + 30 tracks. 

But it did somethings that other kart games didn't:

It has 2D levels that feels like platform levels but were fun especially with a ton of players.
Example:
https://www.youtube.com/watch?v=y9mcBQrR7ws

It had an battle mode that was fun and was less about how many times you got hit but rather about how much damage it did and forces you to think (shall I crash into this character with full speed and causing him a lot of damge but also have some damage myself) and it came with bots.

I havn't played the game in a long time but I remember you could collect fruit to fill up your boost meter, if you fill it up without using any you could use a special and a special existed of 2 choices.  a guided speed bonus that makes you catch up to some contenders or a item that would hit everyone and stuns them for some seconds.   I thought it was clever.

and I loved the music in the game:

https://www.youtube.com/watch?v=OAt_QhUuUOY&list=PL-oFDn_0Gk2wygo2k4g7A4Kj8cuwLTAWV&index=7  reminds me a bit of Police academy mixed with some london orchestra..

Transformers Devastation. My expectations weren't high when I started because I'm not really a huge fan of Transformers G1. I prefer the Cybertron series and movies (sue me) but my God when the game started I was immediately sucked in. The gameplay was wild, intense, and flashy as hell. The music was also fucking amazing. I've beaten this game about 7 times including the ridiculously difficult Prime mode but I had blast every single time.

Trickstyle

https://www.youtube.com/watch?v=YuPk_KWnK_I

It's mostly a racing game but with certain tricks that give you points and boosts. Plenty challenging and for a 1999 game pretty advanced. The gameplay was very smooth and intuitive. It's also tough as balls.

Revolt

https://www.youtube.com/watch?v=Mcxupg5YC9Y

The best fun racer that ever existed including Mario Kart. The graphics were insane back then and they still very much hold up today. It's extremely physics based and extremely tough and unforgiving. Also had a lot of content with alternative versions of tracks and a shit load of different cars.

And Gothic of course.

https://www.youtube.com/watch?v=m4g7WQcEXcc

Best RPG series ever made. No RPG until today could ever emulate the elements that made the games great.

Not exactly obscure but barely anyone talks about the original Fallout. It's my favorite game of all time, a true masterpiece of the genre. I've beat it at least 6 times and it never fails too hook me as soon as I start playing it.

There are other games I really love but I never see being talked about: Max Payne 2, The Godfather game, 24: The Game, the original Ace Combat (Air Combat) and Jagged Alliance 2.

Steamworld Dig and Speedrunners don't get the attention they deserve.

Played Kingdoms of Amalur - Reckoning?

That game was awesome.