Nope, not the Tigercat. The F7F was not rejected by the military Seems to me I did do a quiz on that strange bird not too long ago. Anyway, it's time for more clues. If someone doesn't get it soon, I'll run out since this was supposed to go quickly.
Again, I'm looking for an aircraft:
1) This plane actually was rejected upon it's initial submission to it's home country's military
2) This plane later became so successful that it had seven variants produced
3) Many of the aviation "experts" of the time felt this plane was not as good in the role of a plane it replaced
4) Depending on the variant, this plane could have a crew of one or two
5) This plane is a twin engine design
6) Even with twin engines, this plane isn't the fastest in it's class, nor is it the slowest
7) This plane was rejected(per clue 1) do to what was considered a better, single engine design being chosen instead
8) When this plane was accepted, it was accepted because of two design changes. One of the changes was the substitution of heavier landing gear over the original design
9) Due to this plane's design, it can carry a considerable payload. This can vary by configuration between fuel, ordinance or, in limited cases, small amounts of cargo
Good Luck