The sum of all my electrical engineering knowledge:

fun things to do: take apart a cheap camera. see the round cylinder thing? that is a capacitor. break it off. now, solder some leads to the contacts on the capacitor (i used 1/2" lengths of paperclip) and then bend the leads into hooks. now, take a paperclip and bend it into a shape that nearly mates with the underside of your doorknob (on the outside of the door). this wire will be hidden from the rest of the world. run an insulated wire from this paperclip to the other side of the door and let it be for now. take another paperclip, bend it into a ring that fits over your doorknob on the inside, and leave a hook sticking out for about an inch or so. remember that other wire? hang your capacitor so that one lead is attached to the doorknob and the other to your hidden wire. make sure the hidden wire isn't touching the doorknob. now when anyone touches the hidden wire and the doorknob at the same time, they get a good jolt!!!!! to recharge it, simply touch the capacitor to the contacts on the camera you took it off of (you did remember to mark which lead came from which contact, didn't you?)