Harley Earl designed it. Buick built it
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M18 Hellcat.
Maybe the fastest armored vehicle of WW2, officially it would do 55mph on the road. I've read the accounts of several veterans who said it would do 60mph.
Since it wasn't a tank, the armor was thinner, thus enabling the speed. Also because it was lighter, it was better off-road than most tanks. It was said that during the Italian campain, it could climb hills that the Shermans couldn't and was often used in a direct fire mode.
The M18 looked very modern for its day. And why not? Harley Earl designed it...