Reccomend me some psx hidden gems

Legend of Legaia and Wild Arms are a must own RPGs. I'll add more titles after a bit of time.

Azure Dreams
Brave Fencer Musashi
C-12: Final Resistance
Fighting Force
Grandia
Return Fire
Rival Schools
Rollcage / Rollcage Stage II

Disruptor

• A fun First-Person Shooter.

FireBugs

• It was to be Rollcage 3, but they ended up changing the name later on as far as I can remember, loads of fun.

Future Cop L.A.P.D.

• I guess it could be considered a top down view Shoot'em Up, think of ReLoaded or Loaded, with a twist to it or two, it's fun as well.

G-Police

• It's kind of a shooter, you fly around and get to explore a futuristic somewhat open world city with a futuristic helicopter (or something similar), it was good! Now... I'm not sure if it could be considered a hidden gem; It got a sequel in 1999, never played the second game.

Grudge Warriors

• It's kind of like a car combat game, a lot different than let's say Twisted Metal, each level requires loads of exploration and stuff, it's fun.

Krazy Ivan

• A fun little First-Person Shooter, a bit different from most shooter's at the time, it's its own thing.

Silent Bomber

• I'm not sure if this one's some kind of unknown little gem, but nobody ever mentions it.

Vandal Hearts 1 + 2 - If you're a fan of turn-based RPGs you will love them.

Parasite Eve 1 + 2 - A bit popular so you may have played them already

Deception 3

Valkyrie Profile (jRPG)

If you like RPG with some Monsters Capture/Fusion elements, Jade Cocoon is great !

Kartia and Vandal Hearts are good SRPGs. Alundra is a fantastic top down action adventure game, very tragic story and good puzzles

• Does Suikoden 2 considered a hidden gem? idk, but it's THE best jrpg I'd ever played.
• Saiyuki Journey West (this game is easily one of my favourite turn-based psx games)
• Brave Fencer Musashi
  Since you put Tekken there, I assume you're looking for some fighting games as well? If you are I recommend:
• Tobal 2

And my personal favourite: Klonoa: Door to Phantomile

Gex 3: Deep Cover Gecko

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• Dragon Valor - A pretty good Action RPG

• Hoshigami: Ruining Blue Earth - A very good turn-based tatical RPG. Just a little warning, it's HARD.

• Elemental Gearbolt - An unique shooter on-rails which has a pretty awesome OST as well as some RPG elements

• Gekido: Urban Fighters - Who doesn't like some good ol' beat em' up?

• Kingsley Adventures - A Zelda-like game which I happened to like a lot.

• Medievil 1 & 2 - Those action-adventure games are awesomeness incarnated (I liked the first one more though).

• Psychic Force 1 & 2 - A pretty original (and good, though the second one is way better) fighting game

Vagrant Story and Threads of Fate come to mind but I'm sure there's more.

Bugs bunny lost in time and Legend of dragoon

cant remember what was popular, but these were not liked by all my friends.
Kensei: Sacred Fist
Rival schools
Samurai Shodown
Dino crisis
Gekido
Fighting Force
Die Hard Trilogy
Chase the Express
Syphon Filter
Vagrant Story
Warzone 2100
WipEout
ace combat
time crisis
and the best game of all time : PEPSIMAN

wow, long list
PS. some of them are not worth a comeback, but back then they were a blast.
there is this beat em up game by BANDAI i cant name maybe was japan only so i couldnt find it

Suikoden II, Legend of Legaia, Breath of Fire III & IV

Future Cop LAPD
The Unholy War - I've yet to meet anyone else who has even heard of it
Croc Legend of the Gobbos - not really sure how popular that was
Klonoa Door to Phantomile - I must admit I haven't played it yet, but I've played the second game and loved it.

vib-ribbon

Cho Aniki

Team Buddies

xmen mutant academy 2
it's a great fighting game

Final Fantasy Tactics is often overlooked imo

Apart from lots of adventure games, the fighting game I have always enjoyed the most BLOODY ROAR (much better fighting mechanic than its sequels, believe me).

Battle Hunter and Robo-Pit 2 are quite good games. Sadly, Robo-pit 2 has no cutscenes or music in the western version.