Hrm, in game planes?  
Fighter, I'd have to say P-38.  No doubt Kelly Johnson had a real knack for combining form 
and function.  I think the fact that 3 of his 4 most famous aricraft designs have been shown in this thread (P-38, F104, SR-71 & U-2) attests to that.
Med Bomber?  that's a tough one, can I say mosquito?  love that plane. 
Heavy, B-17 no question.  
Best plane of the 60's F-105 Superchief.  With the 104 being a close second.  
I've always liked the look of the F-15, I could be a bit biased there, because we were stationed at Luke AFB when the Eagle's were first coming into operational duty....my borthers and I would bike as close to the runway as we were allowed, and sit there with our cameras.  About 1 in 3 takeoffs would be a max performance climb out....sweet.  

I dunno, if it flies, I love it.  
 
 Cheers, 
Spitter
It's good to make friends, even if you have to shoot them out of the sky sometimes.