After all this talk of ghost towns im out to make one. I'd prefer no survivors. Are there any towns without essential npcs?

Try the smaller ones, like Karthwestern.

It seems to me that every town has at least one person that can't be killed. But it is sure fun trying.

looks like someone already made karthwestern a ghost town in my game. damn dragons or vampires.

Theres a difference between Towns, Cities, and Villages don't forget. I'm pretty sure that every City has multiple essential NPCs. As for Towns and Villages, you should be able to find quite a few without essentials.