He conceived of alternating current.
He invented the electric coil (every cr has one)
He invented radio (Marconi infringed n his patents)

There are a lot of rumors that he also figured out how to draw energy from teh magnetic fluxuations of the sun and earth's core, meaning free energy. A lot of conspiracy theorists think the technolgy is suppressed. Here is a video showing a circuit that draws energy out of thin air, supposedly designed by Tesla. There are several videos out there showign that you can draw electricty out o fthin air.

If Only.

IN short , today is his birthday

He was indeed a man of the future and gave Thomas Edison a run for his money.