Under-rated.....
Boston III: Gives the A-20G a whuppin' (and a significant number of fighters too).
SBD: Out turns the FM-2 quite easily... Ask Slapshot. Shot down a 262 with one....
TBM: Matches the Hurri IIC in turn radius. Killed jets with this thing... Dives well.
P-39Q: Surprisingly fast. Lethal pumpkin gun. Good maneuverability above 200 mph. Lousy flaps.
P-38L: Used primarily as a bomb truck. I prefer it to the J for its faster roll rate. In the hands of an expert, as dangerous as they come.
P-40E: It's really a P-40K, E models didn't have WEP. With some altitude (potential E), very dangerous.
P-47N: Untouchable up high.
BF 110C: Shocking low-speed maneuverability. Just adequate guns.
SpitIX: Not widely used since the Mk.XVI and Mk.VIII arrived. Not as fast down low, doesn't climb as well either. Gets better as it goes up. Above 25k, it's one of the most dangerous fighters in the game.
Future under-rated...
B239 Brewster. Wing loading nestled in between A6M2 and Mk.V Spitfire. Combined with high CLmax, the Buffalo should be big trouble in a low-speed fight.
My regards,
Widewing