(2) Thomas Edison
The sheer scope of Edison's inventiveness is staggering. The Wizard of Menlo Park held a record 1,093 patents when he died in 1931. Everyone knows him for the light bulb, but Edison also had a hand in the invention of the radio, the phonograph, and an improved stock ticker. His achievements weren't all nerdy science, either; Edison's electric engraving pen needed just a few modifications to become the world's first tattooing machine.
(7) Nikola Tesla
Not since Benjamin Franklin has one man's name been so inextricably linked to electricity. Tesla's major breakthroughs, including the rotating magnetic field, made the alternating current we use in our homes possible. His Tesla coil was a key part of early radios. He's still revered as a god among electrical engineering fans, and he might just have been the most important inventor of the 20th century.
A bitter grudge match over a century in the making! These two had legitimate beefs on both a scientific and a personal level. When Tesla arrived in the U.S. in 1884 with little more than four cents and a schematic for a flying machine, Edison was his first employer. Edison allegedly jilted Tesla on payment, and the two had a falling out. Later, they engaged in a "War of Currents" over whose system of electric power distribution was superior, with Edison backing direct current and Tesla in alternating current's corner. In the end, Tesla got the last laugh. Alternating current brings juice into our homes, and he outlived Edison, which enabled him to slam Edison in the New York Times on the day after his rival's death. Which one's the bigger genius, though?
[See the whole bracket here.]