5. Biff Henderson
From the beginning of Dave's late-night career, James Jackson Henderson Jr. has been by his side, serving as the show's stage manager. But more importantly, the man we call "Biff" has played the crucial role of all-encompassing good guy. Where other Letterman sidekicks are hapless, wacky, surreal or deadpan, Biff is winningly genial. Whether hanging out with the New York Yankees at spring training or visiting a tiny town in Idaho, he's brought a common touch to his taped segments that even our folksy Hoosier host couldn't match. Other people associated with the show are way cooler; Biff is the one guy you'd want to have a beer with.