Audrey Hepburn played guitar (apparently) in "Breakfast at Tiffany's."
A name some older folk may recall is Cliff Edwards, a former vaudevillian and western movie sidekick of the forties. Once billed as Ukelele Ike, he was the voice of Jiminy Cricket in "Pinocchio" and sang the timeless "When You Wish Upon A Star." He and Judy Garland had somewhat parallel careers in that both were extraordinarily talented, very well liked in the movie community, but both were badly used and both undone by alcohol and/or drugs.