The file
A pressurized water gun that ended the squirt-gun era in one summer. Lonnie Johnson, who worked on the Galileo probe, invented it in his bathroom, and by 1991 the Super Soaker 50 was the loudest thing at every pool.
The arms race that followed produced the CPS 2000, which hit hard enough to be pulled from shelves. If you had a Super Soaker, you were feared. If you had a regular squirt gun, you went home wet.
Sources: Wikipedia — Super Soaker