More Efficient Ways of Killing People

The Switchblade.

When completed (target date: 2020), it will
cruise with its 200-foot-long wing perpendicular to its engines like a normal
airplane. But just before the craft breaks the sound barrier, its single wing
will swivel around 60 degrees (hence the name) so that one end points forward
and the other back.

The concept art is pretty neat, too!