Also works as a rare win condition in combos
Admiral Brass, Unsinkable from the Ahoy Mateys deck
Cruel Somnophage Without the Blue side, this needs about three creatures in graveyards to be on-rate (and counting casting the Blue side, arguably closer to five.) Depending on creature density, that may not be too hard
Phyrexian Elesh Norn, Grand Cenobite Phyrexian Jin-Gitaxias, Core Augur Phyrexian Sheoldred, Whispering One Phyrexian Urabrask the Hidden Phyrexian Vorinclex, Voice of Hunger These are only card styles, and to use them, you have to own the actual cards
This four-mana black 3/2 gives a target creature an opponent controls -X/-X until the end of turn, where X is the number of permanent cards in your graveyard