The Sikorsky S-39 was a single-engine amphibious flying boat, with a boat hull suspended underneath a single wing, with a single tail joined to the wing by a pair of booms. The S-39 pictured here, NC54V, is particularly unusual because it served with the Civil Air Patrol in support of its Coastal Patrol anti-sub mission during the early part of WWII. This S-39 primarily served in a search-and-rescue role, working to recover CAP sub hunter planes that went down in the Atlantic.

Mostly I like the S-39 because it looks like someone built a flying boat out of a car. Also the company ended up getting out of the airplane business because aircraft with wings weren't weird enough for their tastes.