My "maid-of-honor" is a guy. What do I call him?
Many couples choose to use the term "man-of-honor" for this, instead. That way, you're still showcasing the honored role in the wedding, but simply replacing "maid" with "man." Of course, you can use any term that you and your honor attendant are comfortable with: best man, bridesman or honor attendant. It's your call, but make sure that your "man" is comfortable with his esteemed title.