O_o (fear)
Most annoying mob

I think it happened to him at some point in his life. Someone crawled into his head and now he has a dual personality

skeletons when i have lag on my computer and witches are sooo annoying when you are trying to kill them with splash potion of instant damage.

herobrine is soooo annoying he gives you nasea, bindness and slowness for 5 min and the bats he spawns are so hard to kill in this situation

I'm not sure why you would try to kill a witch with instant damage potions... And herobrine isn't a vanilla mob, so he doesn't really affect me.
Probably it's because if it jumps in 2 nanoseconds it crawls over your face into your ear to your brain and eats part of it.