well, there're two that can cast lightning. the Statically Charged Sheep, and the Dark Magician.
the sheep is just simply annoying, but the dark magician can wipe your HP on the wall within 5 seconds. it summons skeles, smites you, and sprays wither skulls in your general direction.
i think you ran near the Dark Magician based on what you said :3
Zombie Goku and Skeleton King are other mobs...
Zombie Goku explodes you upwards with TnT effects, and normally it's the drop that kills you. he's really OP v:
the Skeleton King summons a crap ton of skeles, which are defeatable, but it's hard to move with 20+ skeles shooting you...
there's others, but that's all i can recall off the top of my head
EDIT: i forgot to mention that both Zombie Goku and the Dark Magician drain your health (and can kill you) in god mode AND creative mode.