1. Ju-88.
Served for the whole war, in more roles and with more sucess than any other German twin engined plane.
2. Spitfire
Served and saw action over Britain, Germany, France, the Low Countries, Egypt, Malta, the Western Desert, Italy, Russia, Australia, Japan, China-Burma-India theatre, Yugoslavia and the Balkans. Fought wherever the British were, as well as being supplied to the airforces of the USSR, Australia and the United States.
3. Bf-109.
Served and saw action in every German theatre of the war.
4. IL-2.
Ubiquitious ground attack aircraft on the Russian front. Produced in, and lost in, greater numbers than any other aircraft in history.
5. Hawker Hurricane.
Relegated in Europe to fighter bomber status by 1941 and then to ground attack fighter by 1942, the Hurricane still solidered on in numbers and places where it was needed. The defence of Malta, the opening years of the CBI theatre, the Western Desert. Performed admirably as a dedicated ground attack aircraft, straffer, rocketeer, carrier fighter, convoy support and foward observer and liason.
6. P-40 Warhawk.
The mainstay for the USAAF from 1941 until 1943 and still serving in the frontlines in large numbers well into 1944. A poor performer compared to its rivals in the Spitfire, 109, 190, A6M and Ki-43, it was still tough, dependable and brought its pilots home. Handled well, it was still a good opponent and it worked wonders as a fighter bomber in Africa and the PTO.
7. Wellington.
One of the Forgotten Soliders of the second world war. Slow, underarmed and slightly ponderous, the "Wimpy" was also a match for any medium bomber when the war broke out, with the notable exception of the Ju-88. It formed the backbone of Bomber Command until the Streling, Halifax and Lancaster became availiable, serving with ~20 squdarons by the end of 1941. It was also widely used in costal reconnisance, electronic spoofing, submarine hunting and a host of other roles.
8. Yak-9 serise
The most produced Russian fighter of the war. It held the line with reasonable performance and good numbers against faster and better armed German opponents. Outstandingly nimble, reasonably well armed and easy to fly, it was a match for most of opponents as a low level fighter. Specalised versions were made for long range, ground attack, tank busting and high altitue interception. The 1944 Yak-9U was probably the best Soviet fghter above 5000m.
9. Ki-43.
While talk about the Zero seems to alternate between praise and scorn (usually depeding on how much aviation reading you have done) its IJA sister seems to mostly go unnoticed. Possibly the most nimble monoplane fighter of all time, many Allied PTO veterans said that the Ki-43 was a more dangerous opponent than the Zero, with better handling at high speed and generally better manouverability but little in the way of firepower. It was the second most produced Japanese plane of the war and fought furious actions against the Allies from 1942 onwards.
10. Halifax.
The 'other' 4 engined bomber of Bomber Command. Like the Hurricane, the Hallifax seems to have been overshadowded by a slightly better performing and more photogenic rival. The "Halibag" towed the line night after night for BC, dropping huhge amounts of tonnage but also taking appauling losses. It actually performed in more roles than the Lancaster.