Death Ray — a “death beam” Tesla called Teleforce in the 1930s. The device was capable of generating an intense targeted beam of energy “that could be used to dispose of enemy warplanes, foreign armies, or anything else you’d rather didn’t exist”. Never built.
Wardenclyffe Tower — Free electricity for everyone! Who could object to that?
Tesla’s Oscillator — could allegedly simulate earthquakes. Allegedly built, but destroyed.
Free Electricity System — With funding from JP Morgan, Tesla designed and built Wardenclyffe Tower, a gigantic wireless transmission station, in New York in 1901-1902. For wireless communication, however …
The Flying Saucer — an anti gravity “flying machine”. Never built.
Improved Airships — electrically-powered airships would transport passengers from New York to London in three hours, traveling eight miles above the ground. Eight Miles High — et tu Roger McGuinn?
It was long suspected that the FBI literally stole all of his work, research, and inventions that he had in his possession when he died. This rumor has now been confirmed by recent, heavily redacted Freedom of Information Act requests released by the FBI.