Beat me to it. 
Believe it or not, the same can be said for the F6F. Was on the boards prior to Pearl Harbor, although I'm sure the captured Zero prompted some needed design changes.
The first Cyclone-equipped prototype (02981) flew on 26 June 1942 while the first Double Wasp-equipped aircraft, the XF6F-3 (02982) had its first flight on 30 July 1942.
The A6M Zero fighter 'Akutan Zero' wasn't loaded onto a ship bound for the continental United States, until Jul 1942.