Have quite a few games in the collection that are considered rare, here's just a few of them. A mix of rare and/or expensive.

Starting from top left...
Wonder kitchen: A cooking game given away by Ajinomoto to people who sent in the coupons of mayo bottle labels.
Bangaio: A more well known game that seems to go for weirdly high prices even though it's not hard to find.
Bomberman 64: Not the same game as bomberman 64 that the west got, this is a totally different game. It was the last Jpn N64 release so pretty rare nowdays to find.
Zelda collection: Same as the western zelda collection except the manual is in full colour, was released in smaller amounts compare to it's western twin due to it been up on the club nintendo goods page for only a short amount of time.
Coropata: Yup not remotely retro but really hard to get for a sane price as it had a tiny single print run so the prices are a bit mental for it at the moment.
Togepi's adventure: Probably my rarest game, pokemon mini games are pretty hard to find but this one is the hardest out of all. It's seriously rare, i have yet to meet another collector who even has a copy theres not that many about at all.