Hi Ryan,
The General Dynamics/McDonnell Douglas A-12 Avenger II was intended as a stealth replacement of the Grumman A-6 Intruder. It was initially designed to have a higher payload than the F-117 Nighthawk and a true air-to-air capability, but was largely developed in secrecy.
The prototype should have made its first flight in 1991, but the programme was cancelled by the then Defense Secretary Dick Cheney in January of that year, just before Operation Desert Storm, the First (US) Gulf War (or Second Gulf War if you count the Iran-Iraq war of 1980-1988). At the time of its cancellation, there were still a lot of issues with the aircraft, such as development problems with its radar system, the aircraft weighing 30% more than expected, and a unit cost of over $100 million.
The entire programme cost over $2 billion, and produced little more than a full-size mock-up model that was revealed to the public in 1996, five years after its cancellation; tonnes of artists' impressions of what could have been, and dozens of court cases, some of which are still ongoing, a little over twenty years later...