I was wandering around Amazon the other night and I came across Powerballs. They are tennis ball sized balls with a gyroscope inside, and once you spin up the gyroscope the thing generates a lot of force. At max speed of around 15,000 rpm it's equivalent to around 18kg of force.
It looked like fun so I bought one.
It arrived today and I've had a good play with it. My arms ache now. It's a bit tricky to get it started spinning, but the websites and so on assure me that it gets easier with practice. So far I've managed to get it to around 6,000 rpm which already feels pretty powerful.
It lights up nicely too :-)
I still believe that gyroscopes are powered by magic though and I'll always believe this whatever anyone tells me or proves to me with stupid equations.