Some of the Japanese Army Air Force aircraft come to mind, particularly the bombers. I can't agree with the P-40. By most measures, this was a highly successful design. It remained in production through late 1944 and served with distinction in just about every theatre, with more nations than practically any other aircraft. It had it's shortcomings, but used properly it was to be respected. It was a bridge aircraft, in that it filled the need for a modern fighter until the newer designs could replace it. Even then, it continued to soldier on for the duration.
