Ponder / Preordain While the easiest explanation for Ponder and Preordain being on the Modern banned list is that they made Storm too good, and while it's true that Storm was near the top of the format when they were unbanned, in no small part thanks to the power of the one-mana cantrips, the better explanation is that they are simply too good and were keeping Modern from developing its own identity as a format
You cant cheat out expensive cards, but Gandalf adds some super-charged Panharmonicon action to your deck and at minimum gives your commander flash
Zhalfirin riddle 4/4 Illustrated by Steve White Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
Massacre Girl, Known Killer and Syr Konrad, the Grim can abuse all this death to draw cards and obliterate life totals
This price point, however, is just due to the cards collectible nature, rather than any gameplay value