Gitaroo Man. Such a great game, it should be sold out everywhere. I've had mine practically since it came out, but when I see one still on the discount shelves, I almost want to give it a home.
Also, the entire
Harvest Moon series. Granted,
someone has to be playing them other than me, for Natsume to keep cranking them out. But they've always been sleepers, and it seems a little unfair.