For those fighters that did make it into service in numbers, the bearcat and sea fury would get my vote but there were a number of aircraft that would have been even more spectacular if they were not beaten by the jet age.
One of those was designed and built in Australia by the Commonwealth Aircraft factory.
It was called the Kangaroo or CA-15.
Only one was ever built and flown.
During its development in the war years it suffered major engine changes because of lack of supply and was meant to fly with a radial R-2800-57W which was going to give it a top speed at sea level of 400 mph and better than 480 mph at 28000 feet.
Its rate of climb at sea level was 4200 feet per minute and 5700 feet per minute on war emergency power.
By way of comparison the fastest fighter at sea level in 1944 was the Hawker Tempest MK.V at 392 mph while at 28000 ft the spitfire MK XIV could reach 443 mph, the Mustang P51D 434 mph and the P-47 Thunderbolt 402 mph. The Tempest V could reach 437 mph at a much lower altitude of 18500 ft.
The fastest climbers of the time were the Griffon powered Spitfire Mk XIV at 5000 ft per minute and the Tempest at 4700 ft per minute.
Due to government vacillation and supply problems for the radial engine, the CA-15 was redesigned to fly with with a Griffon 125 which would have performed better at lower altitudes with at top speed of 495 mph at 26500 ft.
Still more government **** ups and it eventually flew with a Griffon 61 engine in March 1946, two years after it was intended to.
Armament was 2 x 50cal and 2 x 20mm cannon together with provision for 10 rocket rails or 2 x 1000lb bombs.
In May 1948 Flt Lt J.A. Archer of the Royal Australian Airforce flew the Ca-15 over Melbourne at 502.2 mph at 4000 feet after coming out of a very shallow dive.
Due to almost criminal stupidity by the government at the time, the Ca-15 was scrapped in May 1950 therefore leaving Australia without the only example of this gem of an aircraft.
All that is left is the book I am quoting from and 70 odd pages of details, photos and test pilot reports.
For more info, google CA 15