Ambisexuals are people who can assume either mainstream gender (male or female) at will. Used imaginatively in Son of Man, by Robert Silverberg. Not the same as hermaphrodite. Ambisexuals can become either sex at any time. Handy you must admit, but rather disconcerting if you weren't ready for the body parts to appear. Let's not even go down the discussion path of impregnating oneself.