I am certain I already posted back when this first came out. But for fun, without looking at what I wrote then, I'll play again. It'll be interesting how close this list is to my original list.
In no order (except the P-40 which is my 1st place pick):
P-40 - "best second-best fighter of the war." Held the line while better fighters were defending CONUS and under development. XP-40Q showed what the P-40 could have been if developed, although as much as I love the P-40, I agree with 'why?'
Ki-44 Shoki - after a few scraps, Tex Hill reported to Chennault, "I don't think we can beat these Japs in the air." Less than 2,000 built, but with great performance for the time and PTO/CBI, with bulldog malevolent lines that looks cool.
Fw 190A - so many built, so many variants and models - the world's first true multi-role fighter? - and technologically brilliant.
A6M Zero - aesthetically beautiful. Had a short heyday but never ceased being dangerous even in obsolescent.
Hansa Brandenberg seaplanes - like steviecee wrote, Good looking planes.
Now I'm jumping in the Wayback Machine and comparing to my original post.