Step 1: Parts
- Disposable Camera - You can get a free*, used disposable camera anywhere film is developed
- Soldering Iron
- Copper wire
- Electrical tape
*I've gotten all of mine for free, but I've heard of other people spending up to a quarter for each camera.
Step 2: Take it apart
Step 3: Charge it up
Then hold the button for a few seconds. You should hear a high-pitched whine. When the whine stops your capacitor is charged.
Stay clear of all the metal parts when the battery is in, or when it is charged. You might even want to electrical tape over all but the capacitor contacts.
Step 4: Have fun
Most capacitors are charged from 300 to 360 volts with very low amps (didn't even register on my multimeter) so you dont need to worry about hurting anyone too bad (I've been shocked quite a few times).
If you want, you can even take out the capacitor and solder wires in its place. The voltage stays the same and the shock is constant (as opposed to the quick discharge of the capacitor), but it doesn't hurt quite as bad. I think the trade is worth it. It will still make your arm twitch pretty good.