6. Amy Sedaris
Letterman has said he had no involvement in the hiring of Stephen Colbert as his replacement, but what the current and future Late Show hosts have in common is an abiding love for actress/author Amy Sedaris. A frequent presence on Dave's CBS show, Sedaris is one of the few female comics to really click with Letterman, who has always had an easier time getting chummy with male guests. A sarcastic wit, Sedaris managed to get Dave to open up about his son and his pets. As Letterman told his audience in 2005, "Now what you have to understand about this lovely woman — in addition to being a fine actress and a wonderful comedic talent, she's peculiar. … [She's] joyfully different than everybody else walking around on the planet. That's what makes her special."