I enjoy the shiver that goes down my spine when a character freaks me out completely. I like the uneasy feeling that goes along with the "what if" questions; what if this person really did exist? If I can say the thought of that chills my blood, I've written something really worthwhile.
I can see many of you virtually backing away, bringing up the phone to dial 911. Let me be clear in that I do not admire real maniacs. I'm not some closet killer waiting on the right opportunity. I just enjoy writing dark characters and I like the challenge of creating a maniacal persona that readers will remember long after putting the story down. They may not want to sit next to the person on a bus, but they can enjoy the uneasy feeling such a character evokes.
How do you feel about truly evil characters? What's your favorite fictional maniac?