Just to see the person's reaction when they open their door and are faced with several strangers holding balloons, a giant check and a television camera.
I read an article once about the PCH prize patrol.
There was one woman who was rarely home, so they wanted to surprise her as she was getting out of her car. The only problem was that she could tell that the van was following her, and it scared her, so she was driving like a crazy person to get away, and the prize patrol was driving crazy trying to catch her. She ended up driving to a police station, jumping out of her car and running inside, screaming for help.
On a side note, my college roommate worked for PCH during the summer, and there were times that she had to go down to the room with the giant containers full of entries and pick winners.