Yak9T& U, Ki-61, C-205/202 all tend to be under used, and flown by those who truly understand them.
All of them have a slight handycap of one form or another. Be it short ammo clip, poor cockpit visibility, etc.
My personal favorite currently is the Ki-61. Nose mounted guns, high rate of fire, fast enough to be dangerous, agile enough to get me out of trouble, or deeper into it.