Jack The Ripper for Various and Sundry reasons.
For one thing,we have the same name!
For another,Lordi made a song dedicated to him!
And He Never! Got! Caught!
He had 5 victims that we know about,he probably killed a bunch more that were never found,he left clues,he even sent letters to the police chasing him! 5 victims may not seem like much compared to the other killers on the poll but you have to add in the factor that he was only hunting specific people in a specific area. And of course, he got away with it without revealing his identity,location,likes,dislikes,hobbies(except for whore-killing of course) and he probably died of natural causes years later! So in conclusion,Vote Ripper!!!