The Gray Motor
None we know of
"In 1957, a Russian immigrant to the USA, one Alexei Poppoff, showed Edwin Gray a circuit which he said he had been shown by Nikola Tesla. Tesla in his Philadelphia and St Louis lecture in 1893 showed how loads can be powered when a high voltage source is pulsed by magnetically-quenched sparks – this creates DC pulses of very short duration. Edwin Gray joined up with his next-door neighbour Marvin Cole, who held a Masters degree in Mechanical Engineering and who, unlike Gray, was able to understand the circuitry."