The Vultee XP-54 is quite possibly the oddest World War Two era interceptor craft. The XP-54 has a reverse facing single engine, a large central wing, and a dually supported tail that looks positively boatlike. First some background, the XP-54 is the winner of the Circular Proposal R-40C, a contest to design a fighter of "unorthodox configuration". CP R-40C resulted in the development of the Northrop XP-56, and Curtiss XP-55, along with our hero, the Vultee XP-54. This project was an effort to increase "creativity" and "liberality" among the plane designing squads of the fourties. Basically, the XP-54 is the result of government mandated art.
The XP-54 flew for a total of 63 hours and ten minutes in the entire lifetime of the design. The lack of use in any real combat was the result of deliberations over the Lycoming XH-2470 liquid cooled prop engine. Originally the XP-54 was to be outfitted with the much lighter, and air-cooled, Pratt and Whitney X-1800, but to Vultee's dismay, that engine was promptly discontinued from production. Once the Lycoming engine was decided upon, it too, was promptly discontinued. Vultee proposed modifying the airframe to install the Allison 3420, but alas, the Vultee itself was, as you guessed, promptly discontinued.
If ever you want to resurrect the strangest looking single engine interceptor with a service ceiling of 37,000 feet and a mounting elevator, you're going to want to resurrect the XP-54.