Panzer Bandit: 2D beat'em up with a lot of moves, insane combo potential and cool mechanics. Wouldn't be a stretch to say it's one of my favorite beat'em ups ever, it's a really fun game and you can unlock bosses as playable characters. Highly addictive.
Adventure of Little Ralph: Extremely tough 2D plataformer but genuinely one of my favs of all time. This is coming from someone that used to play nothing but plataformers back then (check my pfp for reference). Very difficult but still fair. Would probably recommend playing on Easy first. The game stops before the ending and doesn't let you finish, but it's an immense help to get used to the game and levels.
Sheep Raider: Puzzle game based on Looney Tune's Ralph Wolf and Sam Sheepdog. Your goal is to sweep the sheep away without getting caught by the dog, which usually involves using the scenario and items in ingenious ways. Each level has a different set of tools you get to achieve your goal, and you must always change your tactics since the sheep are always positioned in a way that only the correct appoach will work for any given level. There's lots of variety here with strategies and items you can use, as well as guest appearences from other Looney Tunes characters. Never been much of a puzzle guy, so i don't have a lot to compare to, but i have no doubt this is by far the best puzzle game i've ever played. Lots of charm and well, it's Looney Tunes! Anyone that grew up watching their stuff should probably give this one a chance.
Mad Stalker-Fullmetal Force: Same developer as Panzer Bandit, same type of game. They actually share a lot between mechanics and stuff, but this one is shorter and has less content. Still a really fun game. It has a Mecha vibe going one which is great for people who love giant robots like me.
Alundra: A game that has lots of similarities with old top-down camera Zelda. At first glance it may seem to be nothing more than a Zelda clone, but oh boy, it's much more than that. You play as a boy that travels to an island and suddenly discovers he has the ability to enter people's dreams. The story actually gets pretty dark and you end up getting involved on the revival of a very powerful demon, but i'm not going into details to avoid spoilers. Gameplay-wise it's very reminiscent of Zelda, but where this game really shines is in the puzzles. Some people call this this one of if not the hardest PS1 game, and i would say it's deserved, all thanks to the puzzles. This game gets really brutal expecting you to figure stuff out, but it's really fun and even i that barely play puzzle games managed to get to the final dungeon without consulting a guide (i had to consult one in the last dungeon because i had no idea what was going on there. It introduces a mechanic and doesn't give you any explanation about it). It's a long game but i enjoyed it very much. If you like to test you brain power this one is for you. Lots of tough puzzles to solve. If anyone intends to play, please play with the un-working designs patch. It's available here at the Repo. When the game was localized they changed the values around and gave enemies more damage and health. It just makes the game really tedious and combat isn't even what you should be looking for in this one anyway.
Sorry, i got carried away. Have fun, anyone that intends to try out at least one of these.