Everyone should play with them a bit but they should be treated more like a delicacy than a staple if good games are the objective
I don't count Ezio, Brash Novice, even though it can become an assassin with enough counters
Creatures : Viscera Seer, Krosan Tusker, Golgari Guildmage, Charnelhoard Wurm, Deadwood Treefolk, Hissing Iguanar, Pyreheart Wolf, Falkenrath Noble, Flayer of the Hatebound, Bone Shredder, Shriekmaw, Indrik Stomphowler, Lyzolda, the Blood Witch, Savra, Queen of the Golgari, Anger, Sakura-Tribe Elder SekKuar is particularly nice with effects that sacrifice creatures, since you get the effect plus you get a bonus 3/1 creature to go along with it
Cards like Myrkul, Lord of Bones, Teysa Karlov, and The Meathook Massacre have amazing interactions with The Sibsig Ceremony