>>Is this the engine that was used on many American fighters, such as the
>>Chance-Vought F4U Corsair, Republic P-47 Thunderbolt, Grumman F6F
>>Hellcat, and Grumman F7F Tigercat (which had two!)? Any others?
>
>Lots.  F3F3, F4F,

Uh... didn't these two planes enter service before the Pratt & Whitney
R-2800 Twin Wasp was even designed, much less produced? F3F was a biplane,
and the F4F was basically the same fuselage and engine, with a single
mid-mounted wing.

>                 TBM-Avenger, B-17, B-25, B-24, B-26, A-20

As I recall, the B-17, a prewar design, originally had four 750-hp Hornet
engines, I think by P&W. Many revs later, it still had the same engines.

>If you want really weird - check out a WW-I vintage aircraft in which the
>cylinders (and propellor) rotated and the crankshaft stood still...

The Nieuport-17 that Rickenbacker flew, and the Fokker Dr1 Triplane of
Red Baron fame, had such engines ("rotary" instead of "radial") among
others. Gyro forces were so heavy in them, that if you turned right, the
plane pitched upward; turn left, and it pitched down. They also had no
throttle-- ran at full power all the time. Landing was interesting-- the
pilot had to keep cutting the ignition switch on and off to let the plane
settle to the grass (paved runways? We don't need no steenking paved 
runways)
while maintaining power to go around if necessary.

There's already a weird engine in the V6anagon... wait for the debut of
the R28anagon this year! Coming soon, to a whacko list member near YOU!
I may have to cut a larger hole in the engine hatch, I guess... bigger
gas tank too.    :^)