How about the Sergeant York anti-aircraft system? The military spent a fortune on it only to scrap it almost immediately. Another good candidate is the B-1 bomber. It was supposed to be stopgap plane between the B52 and the Stealth bombers. However, by the time they got most of its problems worked out, the Stealth was almost ready for deployment. The Carter Administration cancelled the B1 program, but the Reagan Administration decided to continue its development.