All the rare cards in the Base Set were printed in equivalent numbers (not counting those that were packed into starter decks), so in principle, there isn't a single rarest shadowless card
For serious sellers, the best advice I can give you is to research and track market trends using the online tools I provided to chart sales history regularly, so you can set optimal pricing for your cards
Share, the two-Energy cost of this attack becomes essentially just your normal Energy attachment per turn, in a mono Terrakion deck running four Exp
Artifacts have strong reanimation capabilities, also - they're easy to return from the Graveyard
The rogues deck, dubbed Sneak Attack, has a subtheme of milling opponents with the addition of cards like mill all-star and classic Oona, Queen of the Fae