The 2 rarest GBA games are Math Patrol and Word Safari, both by the same company. They weren't on a single rarity list until a year ago, and only 2 of each have shown up on eBay in the last 4 years. There are a couple on Amazon right now, but there wasn't a single copy on Amazon for 3 years up until roughly a year ago. Thread's a little old, but figure I should give everyone a heads up, since this still isn't on a lot of rarity lists.