Try to imagine your in a B-17 and a ME-262 is coming at you with 4 x 30mm cannons and knowing your gun turrets cannot traverse fast enough to get them, a couple of those rounds through the nose and there is a good chance that the 4 crew are gone Pilot, Co-pilot, Bombardier and front upper turret gunner guess it was a terrible end.
The Red tails decided the only way to beat the Jets was to get line abreast and have them fly through a scatter gun effect of all those P-51 50 cals spitting lead a desperate solution to a desperate situation but no matter what I reckon 2 positions in bombers stood out for sheer guts Tail gunners in both the B-17 and Lanc the last a bit more because unless you had a chest chute on your parachute was outside your turret in the Lancs fuselage.
And the last would be the ball turret as you were surely hanging in space with not much between you and a very long drop to the ground either way all crews and fighter pilots had guts especially when you think of Schwienfurt and the Rhur valley