It depends on the price range you want to spend. There are some good puzzle games available out there for not too much like Puyo Puyo 2, Bust a Move and Gunpey. The Clock Tower port is fun but it moves a little slow. If you want an action game that's on the low price side Buffers Evolution is good

Thank you!

If you're willing to spend more the Klonoa game is a lot of fun and Pocket Fighters works pretty well for a grayscale 2 button fighter.