I really get a buzz when I take someone up that is a bit dubious at the size of the plane, what to expect etc, and is a bit nervous. You take them up fly around pointing things out as they sit in silence snapping away with their camera (the last lass I took up used three films in 30mins!) and when they get back they have a huge grin on their face asking when they can go up again
I also feel a little a little proud when they say "I wish I could fly a plane"