I actually like the P-39...have done ever since I was a wee one and saw an article by Ray Rimell about building the Monogram 1/48 kit. I just HAD to get hold of that kit. It was so cool, with the ability to leave panels off to display the engine and gun bay, and leave the cockpit door open.
That said, there are a great many aircraft that I really, REALLY like but which weren't great performers: Buffalo, Skua, Whirlwind, Vildebeest, Wellesley, Lysander, A-17, Defiant, Blenheim, P-66, P-35, P-36, Fokker D-XXI, CW-21 etc etc. I'm just objective about their relative strengths and weaknesses. For me, the more interesting part is the courage of the crews who flew them.