Zapzard

A neutral mob that spawns in the savannah. It's nocturnal so during the it day sleeps while at night it hunts its prey, zombies. If you sneak past a sleeping zapzard it won't be alerted, but it will attack whatever woke it up and kill it before going back to sleep. It looks like a large, yellow chameleon with a curled up tail. It stands on its hind legs in a very slouched posture. It's two blocks tall and three blocks long, not counting its horn, which is just under a block in length. From this horn it can shoot a bolt of lightning at targets that will momentarily paralyze them in place while the zapzard approaches to bite them. If the target is in water when the bolt hits, it does massive damage. During the night it will hunt down only zombies, ignoring even players, but will retaliate if attacked. It's meant to be an apex predator, so it hits hard and can take a hard hit. 

It's actually possible to tame these mobs with rotten flesh so they don't attack you, but it can take full stacks of rotten flesh to tame it, and even then it's not exactly obedient. It will do its own thing the same way tamed foxes do, but can be coerced to follow with rotten flesh. It will kill anything that hurts its owner. On death they drop a fair amount of experience, and a zap horn which can be used to brew potions of paralysis, which makes someone paralyzed for a few seconds, so best used for splash potions and tipped arrows.