From permanent heavy Wheels & Cantrips to Graveyard decks, there are a lot of things that can benefit from this type of effect.
Loxi: Being naturally colorless helps this a lot, as it can realistically slot into quite a few archetypes. I think this is a great include in most Commander Decks also, because you can easily get this trigger and then you have a 100 card singleton deck to work through that will start giving you more and more mana. Marcy: 3 mana looting that then turns into a land that can generate huge amounts of mana, especially in decks that put a lot of things into your own Graveyard. Credit: Wizards of the Coast Matzalanti, the Great Door / The Core
