Whenever they knock on my door, I tell them they can't talk to me unless they want to talk to a dead person. When they look at me like wth (oops they don't believe in hell either) I tell them I took several units of blood after a bad car accident and wouldn't be alive if not for that. That shuts them up and they walk away.
http://en.wikipedia.org/wiki/Jehovah...d_transfusions