Wherever you have gigantic, powerful creatures with wild abilities, you'll see demand
This normally isnt too much of an issue, but surprisingly mechanics like energy, transform, flashback and madness have never had their fair shots, achieving varying degrees of success
Get Glarb onto the table and this Noble Frog Wizard will start sucking out lands and casting big spells all on his own
Zen Takahashi Unlike the other cards on this list, Crashing Footfalls is exclusively played in one deck, but it is also the namesake card of the archetype, as the whole deck revolves around the card
Seedborn Muse and Vedalken Orrery are already annoying to play against because of how powerful they are, and Prophet of Kruphix combines those effects into one card
You can switch closers or tweak the answer suite without rebuilding from scratch