How can you leave out The Boulton Paul Defiant? It was a WW2 two-man fighter fitted with a turret, its armament mounted in the top of the plane behind the pilot. Soon, the pilots of Me 109s discovered that they could attack the plane head on, or from below, and blow it out of the sky. Defiant losses soared. It was completely withdrawn from combat in 1942. Yeah, that freakin’ bad.