A light asymmetric capacitor, in its standard amateur form a triangular balsa frame carrying a thin wire above a foil skirt, which rises off a bench when tens of kilovolts are applied across the gap. Thousands have been built since the design circulated online from about 2001, and the flight is real and easy to reproduce.
What makes it fly
Corona discharge at the thin wire ionises air molecules, which are accelerated toward the foil and transfer momentum to the neutral air they collide with on the way. The result is an ion wind and a reaction thrust, and it is well characterised: NASA and Army Research Laboratory work in the early 2000s measured the thrust, attributed it to electrohydrodynamics, and found it collapses as the pressure drops.
Why it matters to the argument
Because it is the Biefeld-Brown Effect in the hands of anyone who wants to test it, and because Paul LaViolette reached the same conclusion about it that his critics would. In chapter twelve of Secrets of Antigravity Propulsion he writes that electrostatic ion-repulsion effects appear to dominate over electrogravitic effects in lightweight devices producing a nonlinear field, and that the same applies to the lifter experiments. That is an author reporting a result against his own case, and it is the reason the site’s Electrogravitics bench has a vacuum control on it.
Connections
Biefeld-Brown Effect · Electrogravitics · Townsend Brown · Paul LaViolette · Secrets of Antigravity Propulsion · Cady ONR Report 1952 · Tom Turman · Anti-Gravity · Project Winterhaven