As a Aviation nut and worker/owner. I have thought about this a lot!! So I group mine into catagorys.
Of all time:
The C-47/DC-3. D-Day, berlin airlift, China-Burma, Korea, Vietnam.......she has done it all!
Battle of Brittan..............Mk.1 Hawker Hurricane, though not as "pretty" as the spit, the hurry was in greater numbers.
Pacific....................F4U-1 Corsair by Chance Vought or a FG.......by Good Year.........."whistling Death" or Bent wing black bird...........soldiered on to korea, just plane pretty!!!
Europe...........some say the Mustang, but I would need to go with a bomber on this one and say the B-17. What else is needed to say, its built by Boeing!!
Korea................North American F-86 sabre jet,,,,,the dawn of the jet age!!!
Vietnam...........I am tied between the C-130 and the UH-1..............both equally valuable!!!
Best Trainer................Naval Aircraft Factory N3N-3. Only 816 built in 1940, by the navy, its the only mfg. airplane where the engine and the airframe were built at the same facility. The last Biplane to serve with the US military...........the last being retired in 1959 from NAS Annapolis..............(this has been a plug for the N3N, out of 816, about 100 exist and about 55 still fly. We have one of these!!!!!