You wouldn't think it from first glance, but a Power Ball is actually a carefully engineered piece of kit originally designed to improve the wrist muscles of those who regularly use it.
After initially setting the inner section spinning, rhythmic circular hand and wrist movements not only maintain the rotation, but also make it steadily faster. The increased centrifugal force makes it harder to keep the Powerball spinning at the faster speeds. PGA Tour golfer Padraig Harrington has been known to use the Power Ball to improve his wrist strength.
The reason Power Ball gets very addictive indeed is due to the rev counter on the top. That means you get a high score, and will probably want to beat it as time goes on. It also means that other people, who witness your Power Ball antics and see your high score, will call into question your muscular capabilities before sneering and snatching away the Power Ball to consign your high score to history.
Needless to say, male adult humans are the biggest fans of Power Ball's mix of strength and scoring, but anyone can do it. Once you get over the initial hurdle of starting the gyroscope (there are two main ways - flicking your thumb down the wheel, or using the provided cord to set Power Ball in motion like you would an old lawnmower), you are compelled to beat your last mark. Perhaps the gentle hum of a Power Ball subconsciously draws you into continued play. More likely, it's the fact that no one calls you a pansy and 11,532 is the score of a legend. Either way, Power Ball genuinely is hard to put down once you pick it up.