Nikola Tesla (1856-1943) is possibly the most famous pioneer of electricity and electromechanical devices. His patents in motors, transformers, radio, robotics, logic gates, x-rays, turbines and VTOL aircraft revolutionised industry and helped usher in the second half of the Industrial Revolution. These days he is remembered more for the Tesla Coil and arcing electrical discharges.
However, toward the end of his life his behaviour became more erratic. He was convinced that aliens were communicating with him. During this time he had a number of ideas inspired by early quantum physics, including long-range wireless power transmission, particle beams, teleportation, anti-gravity, time travel - ideas straight out of Science Fiction. But when Tesla died his hotel was ransacked and his research stolen. No evidence of his later research was left. Many conspiracy theorists suspect the U.S. Government stole his work - it's widely rumoured that he was working with them on particle beam technology before his death. Some even believe that Tesla's later ideas were beamed to him by aliens.
Interestingly, Tesla also conceived of an ion-propelled aircraft that would have no need of propellers, ailerons, wings or an onboard fuel source. The appearance of this aircraft was envisioned as taking the form of a cigar or saucer.