Most maneuverable fighter of WW II?
My guess would be the Japanese Mitsubishi A6M Zero fighter. The plane was very light and manoeuvrable. The Japanese Government asked Japanese designers to design a fighter that could fly huge distances fight a dogfight or battle, then fly back home. All Japanese designers except one believed the aircraft asked for was unachievable but Jiro Hirokoshi managed to design a plane that could achieve all that the plane had to but at the cost of no armour to protect the pilot, no self sealing tanks, and a new top secret duralumin developed by to use as the planes very thin outer skin. The Plane could fly huge distances no other fighter could fly and outmanoeuvre any fighter around at the time. It first saw service in China with Japanese forces fighting there and when news filtered back to America about this new aircraft no one would believe such an aircraft could be built. Until mid 1942 the Zero had a kill rate of 12 aircraft to every one of theirs shot down. When the Americans first took them on in the pacific they were amazed as the Japanese could fly huge distances, shoot down lots of US planes, then fly home. The American aircraft were not even a close match and they paid heavily. The Americans formed a special engineering unit whose job it was to find the few downed Japanese planes and try and make a flyable machine so the allies could learn of its abilities and weaknesses. The Wrecks were brought back to Brisbane, Australia and in a special hangar were painstakingly rebuilt to flyable condition and the allies finally discovered the secrets of the design and then started to develop tactics so allied planes had a better chance in a dog fight. Finally by mid 1942 better allied aircraft and an understanding of where the zero was vulnerable started to see the zero's manoeuvrability start to not be enough in a dog fight with the latest American planes with pilots that understood the zero's weaknesses in certain manoeuvers. The planes lack of armour and self sealing fuel tanks meant if you could hit the aircraft it quite often took little to destroy it. It also suffered as all control surfaces were cable operated and very hard for pilots to operate if manoeuvring at speeds over about 190 MPH. The plane was much harder to control at speeds over 190 MPH so the American pilots knew the zero was at a disadvantage at higher speeds as its manoeuvrability decreased with speed, where to aim at to have the highest chance of killing the pilot or causing it to explode by shooting out the fuel tanks. The plane's design was limited in its ability to be strengthened to give it more protection from hits received, or increase speed and manoeuvrability. It could only fly just over 300MPH which was fine at the start of the war but with Allied planes being able to fly at closer to 400MPH, take quite a bit of battle damage, and with improved manoeuvrability and knowledge of the zero's weaknesses the Zero was no longer the best plane for the job
The Japanese Zero. It could outmaneuver anything the allies had in the Pacific Theater when the war with Japan began. [See source.] A reason for that is because it was comparatively light in weight for the power of its engine. Check this out: "Every possible weight-saving measure was incorporated into the design. Most of the aircraft was built of a new top-secret aluminium alloy developed by Sumitomo Metal Industries in 1936. Called "extra super duralumin" (ESD), it was lighter, stronger and more ductile than other alloys (e.g. 24S alloy) used at the time, but was prone to corrosive attack, which made it brittle. " [Wiki] But in being light, it also had a big failing. If it did get hit by allied aircraft, it would fly apart. That is, it didn't take but a few bullets to bring it down in a spectacular ball of flame. Later in the war, the allies had the P-38 and F6F as their mainstay fighters. And these could out maneuver the zero in most cases, but not all.
Discounting a few biplanes that were never "air superiority" aircraft, the Mitsubishi A6M Zero and Nakajia Ki-43 Oscar were arguably THE most maneuverable mainline fighters of WWII but they were not robust, not particularly fast, not good in a dive nor were they effectively armed. Pilots who flew both claim that the Ki-43 was the better of the two. All in all they were both exceptional aerobatic aircraft but not very effective fighters in the long run. In Europe the Macchi Folgore could out-turn everything else on that side of the world but suffered the same flaws as the Japanese fighters. The most maneuverable Allied fighters were the Supermarine Spitfire and YAK-3 and better overall aircraft than the A6M and Ki-43. The Bf-109 was no slouch either, particularly the 'K' variant which was at least the equal of the best Spitfires, but it suffered from poor visibility, a distinct disadvantage in a dogfight. No American planes can be considered contenders in the maneuverability department, not even the vaunted P-51, but they excelled in other ultimately more important ways, as did many other aircraft on all sides. Tail-chasing, tight turning type dog-fighting turned out not to be the best method of achieving air superiority as it was in WWI.
My vote goes to the Fiat Cr42 biplane used by the Italians. With that much wing you are pretty much guaranteed to be able to out-turn anything. Honourable mentions to Gloster Gladiator, Mitsubishi A6M Type Zero fighter, Nakajima Ki-43 Hayate, Macchi C200 Saetta, and Nakajima Ki-27 Otsu
V173. Had the lowest stall speed & could turn tighter than any other plane. But very few were made. It was a concept plane. Made to prove certain consept's of flight. The Buffalo was one of the best. Till you hung stuff from it like bombs & such.
Ki 43 Oscar as something widely produced and used throughout war, just a bit tighter turning than zero because lighter. Biplanes of various makes fairly good but of limited use. Yak3 was a chopped Yak 1 that had to get bigger engine or cut down weight to handle BF109, very good below 5000 meters and BF109 pilots warned about trying lower level dogfights with it
https://en.wikipedia.org/wiki/Fieseler_Fi_156 Though not a fighter. So popular both Rommel and Montgomery had one.
French ace Marcel Albert thought the Yak-3 to be better than P-51 and Spitfire. The F6F was probably the best carrier-based fighter. The Focke-Wulf FW-190 and P-51 (not the Allison-powered version) were nearly equals, and in my opinion tied for best fighters overall. The Yak-3, however, was small and light with a 1,300 HP engine, and very likely the most maneuverable. It could get on a rival's tail in a single turn, and was nearly impossible to shoot down with a good pilot on the stick.
Polikarpov I-15 or I-153. Both had unrivalled turning performance. However, against faster and better climbing and diving aircraft they were no match.
On the Western fronts probably the Spitfire and Messerschmitt bf019.