Genshi no Kotoba, I have no idea what this game is about, I have never played it. I just have a copy laying around.
Space Fishermen, cartoony fishing in space. Published by Sony themselves back when they weren't afraid to try new off-beat things, remember that polar bear singing game?
Sagashi ni Ikouyo, I don't speak Japanese so I haven't been able to make much progress in this one. It's an early RPG for the PS2 published by Sony. It kinda feels a bit like King's Field except not.
There was also all those games starring Sony's mascot Toro which use real life backgrounds and 3D characters, they are bizarre since I can't understand shits, I guess that they aren't actually obscure in Japan.
Oh and there was that one microphone input, japanese PS2 game with weird 3dcg art done by John K.