All of the cards Im going to discuss can be obtained for less than $5, most can fit well into multiple archetypes, and most are featured in fewer decks than comparable cards registered on EDHREC
7 Hurska Sweet-Tooth Anime - $19.02 A delightful anime card from Jumpstart Foundations, Hurska Sweet-Tooth has some amazing little details in the art that collectors will love
Eldrazi Temple as a multi-deck staple
Hullbreacher would be a very playable Merfolk without the treasure or the draw denial, but having both was enough to secure Hullbreacher an exclusive spot on the MTG Commander banlist
Rarity is another major factorfinding first edition cards, which were the earliest printed, are the trickiest to find and by far the most expensive
Whereas if you saved it, because of duplicate protection, that pack would open a Rare you didn't have yet