Qutie a few
Probably all of the WWII single engine dive bombers and two-seat attack planes had the gunner sitting backwards, as did the torpedo bombers like the TBM. It was a very common arrangement.
Some examples:
Il-2 Sturmovik attack plane
SBD Dauntless dive bomber
Avenger torpedo bomber
Also, as Lee pointed out, virtually every bomber with a tail gun had the gunner sitting backwards. This went all the way from the B-17 to the B-52G. The B-52H had the gunner sitting with the rest of the crew.