Wings

The explanation is a little handwavey, but apparently sound waves can be used to break up laminar flow on airplane wings and thereby increase lift by as much as 20%. That said, airline travel already sucks enough without turning the whole airframe into a sonicator, but you'd think the military would be interested. On the other hand, wing deicing isn't an issue anymore.

I wonder if this would work for sails and propellers as well? By adding small resonators (whistles is the technical term, I think) on a foil, the surface could vibrate itself, which could make windmills more efficient. Thus enabling Holland to pump itself dry faster.