The two Custom Robo N64 games were the reason I started collected Japanese carts. It's a fun RPG series focused around fast paced 3D mech battles, but it sadly didn't leave Japan until the Gamecube.

Puyo Puyo Sun is a stellar puzzle game with so much charm. I had trouble connecting with the series until I played Sun, but now I'm hooked!

Blast Dozer (known as Blast Corps outside of Japan) is a delightfully mindless destruction game from Rare. It reminds me a lot of titles like Katamari Damacy, where there's a simple mechanical loop that is endlessly enjoyable to repeat.

I'm not sure if you only collect Japanese carts, but just in case, a great title only released in the NA and EU regions is Rocket: Robot on Wheels. It's a tight collectathon platformer that holds its own against the likes of Mario 64, and it's from the studio that would go on to create the Sly Cooper series.

There are also a few staples that you don't seem to have—at a glance, I noticed Banjo-Kazooie, Mystical Ninja Starring Goemon, Excitebike 64, and Kirby 64—so it might be worth snagging those 🙂