The character Pie’o’pah from Clive Barker’s Imajica has a sort of “third” genitalia which can both penetrate and be penetrated. Through the story, the main character is kind of magically seduced by this, initially revolted, but it becomes a point of personal growth which helps unlock his true potential. It’s a really cool and weird (and long) story with some pretty ahead-of-its time pontification on trans and non-binary identities.