Obscure title you are in love with.

[Takahashi2212]

Putting some respect out there for Ghost in the Shell, Panzer Bandit, and Jumping Flash! (notably the 3rd game).

Also the Japan exclusive Tales of Destiny: Collector's Edition remake for PS2 is the best way to play the already obscure Tales of Destiny.

Berserk Millennium Empire Arc: Chapter of the Holy Demon War for PS2 is a dope action game set in the Beserk universe. It's got a cool upgrade system, and a cool enemy system, wherein there are a set number of enemies in a given level, and by replaying them you can rid a level of monsters entirely.

Battletanx: Global Assault for the N64 is the 2nd and final game in the Battletanx series, notable for having a fun multiplayer mode and an absolutely bonkers story about a world where nukes have ravaged the Earth and all major countries are now at war over the world's women (now called Queenlords) since the nukes somehow caused the population of men to women to dwindle to 10:1.

Astro Boy: Omega Factor (GBA) is a shooter made by Treasure, makers of Gunstar Heroes. It's incredibly fast paced, and has got some great music. It actually very reminiscent of Gunstar Heroes so if you like that game, I think you'll like this one.

Gunstar Super Heroes (GBA) also doesn't get enough love. IMO, it's better than the first one.

[Psychospacecow]

Gunstar Super Heroes was legit. Loved the character designs, hated the devil mechanic as I tended to accidentally agree to it.

[Colossus]

Gunstar Super Heroes was legit. Loved the character designs, hated the devil mechanic as I tended to accidentally agree to it.

Was? No. Still is.
FIGHT ME IF YOU THINK I'M WRONG

[psyducklover13]

I LOVE some of the obscure games on Taito Legends 1 and 2.
Favourites of mine are Cleopatra Fortune (a puzzle game where you have to surround gems etc... with blocks), Puchi Carat (essentially Breakout meets Bust A Move), Qix (where you must draw blocks to fill the screen while avoiding enemies)...the list goes on.
Go get Taito Legends 1 and 2 - classic arcade games that are sadly quite obscure nowadays.

[psyducklover13]

Just thought of some more:

-> Vib-Ribbon for the PS1 - A rhythm game where you control a rabbit avoiding obstacles on a line (to any song you have on a CD no less!) Thankfully less obscure nowadays as I think it's on the PS Store.
-> The Net Yaroze games on the PS1 demo discs - fans could make their own small games and get them on to demo discs. Results, however, vary from the amazing Time Slip and Pushy IIb to the laughable Engrish of Terra Incognita and The Incredible Coneman with its unceasing bass riff.(Caddicarus has reviewed a whole bunch of the games).
-> Mario's Picross for the GB - fun puzzles and Mario - why didn't this game catch on? Why? Also it's also on e Shop so do have a try of it!

[Arjahn]

Fistful of Frags is a tiny source mod that plays as a really fun cowboy FPS, highly recommend.