[XB-49]

What about a "Old 666" weapon mod for the B-17E.

http://en.wikipedia.org/wiki/Old_666

http://www.youtube.com/watch?v=KO-u2nE_Cjw

It didn't play a big part in the war but you've got to admit, surviving a attack by 15 Zeroes and 2 Ki-46 Dinah's is quite impressive.