" " A girl enjoys the Slip 'N Slide on a sunny day. This is one toy best left to children -- unles you want to make one with an extremely long slide. Daniel Haug/Flckr/Getty Images

Since Wham-O first marketed it to consumers in 1961, more than 30 million Slip 'N Slide toys have been sold. A Slip 'N Slide is a 16-foot (5-meter) sheet of plastic with an inflatable "stop" at one end. There are small holes running the length of the sides, so that when a garden hose is attached, water spouts through the holes, making the plastic slick. The player slides down the wet sheet on her stomach, enjoying hours of cool fun on a hot day [source: Wham-O].

But the fun is meant for kids only. In 1993, the Consumer Product Safety Commission issued a warning about Slip 'N Slide use by teenagers and adults. Turns out, the slide wasn't long enough to accommodate their size and weight. The abrupt stop at the end, in some cases, resulted in permanent spinal damage. At the time of the warning, one teenager and seven adults had become paralyzed or received neck injuries after playing on the slides [source: CPSC]. The Slip 'N Slide was taken off the market, but it reappeared in the 2000s, with a prominent warning on the box to indicate it is for ages 5 to 12.