I'm curious if you guys know. I'm not completely sure what the rarest is, but here's some ideas.
It's a Pikachu Illustrator. Only 6 were made and they were given out after a Japanese contest. One sold for $20,000.
It's Espeon (Star). It's in the Pop 5 series. It is the last star card to be made (along with Umbreon). There are only two for sale on eBay: one is $450 (English) the other is $2,499 (Japanese).
Umbreon (Star). 2 available on eBay. One is $650 (English) and another is an auction currently at $75 (English).
It's a Pikachu Illustrator. Only 6 were made and they were given out after a Japanese contest. One sold for $20,000.
It's Espeon (Star). It's in the Pop 5 series. It is the last star card to be made (along with Umbreon). There are only two for sale on eBay: one is $450 (English) the other is $2,499 (Japanese).
Umbreon (Star). 2 available on eBay. One is $650 (English) and another is an auction currently at $75 (English).