Howling Hag, or if you prefer the witch from Army of Darkness where Ash says, “It’s a trick–get an axe.”
Why is this monster great? Because of the debate that always occurs with PC’s going “old lady we need to rescue, or hideous trap?”
Why some monsters are better than others
Strange Vistas 
Humans make the best monsters for this very reason. Evil wizard threatening the world? He’s the guy over there in the white robe, tending to his orchids and sipping Pinot Noir.