Edit : j’avais oublié celui-là.
Although sadly never making it to full service, the Multipurpose Security and Surveillance Mission Platform (MSSMP) clearly had a lot to offer. In addition to a cruising speed of 80 knots, a three hour operation time, and an 8,000-foot ceiling, it was also shaped like a flying saucer, scientifically proven to be the shape most able to inspire giggles in enemy troops. While dexterous, the ducted-air unit has been supplanted by a variety of cheaper, more disposable UAVs. Perhaps the most surprising thing is that ducted flying machines fly at all.
PENTAGON’S FLYING SAUCER [DefenseTech]