They haven't been around me, in, I'd say about 15 or 16 years. I scared 'em off. It was immature and stupid, but it worked.
At the time, I was a teenage kid and still living at home with my parents. Their house had this big, wide window in the front, so you could see who was on the porch/in the front lawn. I saw a man and a little boy approach the house and thought they were JW's by the way they looked.
They knocked and I opened the door to them, but didn't let them in. Before they had the chance to start their rambling, I asked, "Are you Jehovah's Witnesses?" I immediately turned my head and shouted, "Mom! Dad! The human sacrifices you ordered are here!" They probably thought, "If the kid is that creepy, imagine how bad the parents must be!" because when I turned back to them, they were scrambling to get back in their car.
I swear, no JW ever came back to their house or mine--I live just across the street now. They avoid the entire area like we're the Munsters or something. True story.
But if one ever did come back, I'd reply with something more mature like, "No thanks, but I'm happy the way I am," and then shut the door.