[Doug G]

If charged up at the max rating of 40 VDC - I don't think they will cause anyone that much harm. Resistance of people is on the order of 50,000 ohms - 500,000 ohms. Ohms Law says Current = Volts/Resistance, therefore... at 40 Volts and 50,000 Ohms, Current should be around 0.0008 Amps, which won't do much. It won't get your attention until you get up to 10 mA or higher. Maybe on your tongue will the resistance be low enough to give a good tingle. I use .1 Farad capacitors in my physics class and we charge them up with 9 V and the kids handle them without any shocks; they like putting tin foil on the terminals and watching sparks.

Tesla Coil = NO (Voltage is way to high on a Tesla Coil)

Many of the other ideas mentioned just won't work with this voltage rating of 40 VDC. You can charge it up at 6 V and run a DC item for a while. I bet it could run an iPod Shuffle for a little while??

Power stored in a Capacitor is P = 1/2 * C * V^2, so 1/2 * .025 * 40^2 = 20 W in each Cap if its fully charged up to 40 V.