64mm x 89mm card sleeves Gamegenic Inner (64mm 89mm) (100 Sleeves Per Pack) – Eclipse Games Pty Ltd These are used inside standard sleeves (sleeve WINTRA 600 Count Precise -Fit

PSA 10s sell in the $250 range

I know a lot of M:TG gimmick cards also do something like this where they're on their side

Fighter Class Here is a supplementary enchantment to the Colossus Hammer deck that can tutor for an equipment at play for just two mana, which is similar to Stoneforge Mystic effect

Maestros Ascendancy is a fun Grixis colored option that will, anytime on your turn, let you cast an instant or a sorcery from your graveayrd by sacrficing a dork in additon to it's other costs, which is pretty cool from where I am sitting

Essentially, it can always be the best card on the board, unless that card is a land, which is highly unlikely outside of a few examples