If you wanna keep it simple and turn cardboard sideways, Krenko is the one
Once Zacama, Primal Calamity is on the field, it can act as removal for artifacts and enchantments, as well as creatures
Hedron Crab is great for example, because it is a seriously quick win con in the landfall deck but also helps enabling dredge strategies
Generally, in my creature decks, I only really want this kind of a mana advantage if Im using it to end the game doing something like activating Ezuri, Renegade leader multiple times to attack for lethal
#8: Combustible Gearhulk / Verdurous Gearhulk Oh, youre laughing now, but believe me when I say the kind of deck that this creature goes in is marvelous