Some stars are happy to show their faces in commercials, lending their celebrity to endorse the products they truly believe in, as Tina Fey is doing with that Garnier Nutrisse hair dye, or Matthew Broderick did with his Super Bowl riff on Ferris Bueller for Honda. Others try to keep a lid on their shilling by doing it only overseas. A third class is prepared to do TV ads — if all you hear is a disembodied voice. But if a celebrity's not willing to show her face in support of a brand, can we REALLY believe it has her full endorsement? Here we've collected a list of stars who've provided voice-overs in commercials, considered what their work tells us about the products they've promoted — and, for good measure, ranked them according to how likely they are actually to make use of them, from most likely to least likely.