Kids like water guns.  Kids LOVE Super Soakers.  In fact, according to InventionStatistics.com, Super Soakers is a $400 million business.

This post is more like an extended story under a Snapple bottle cap rather than legal analysis, but I think the story is a fun one.  So how did this invention even come to fruition? Apparently, Dr. Lonnie Johnson, a nuclear engineer, was tinkering at home like many engineers do. Specifically, he was doing some work on a heat pump at home that used water instead of freon.  Turns out the pressurized system he used actually worked much better as a high performance water gun.  Not bad for an alternative embodiment!

As a part time inventor, it took eight (8) years before the gun was finally introduced to consumers.

Patent available online here.