Zach Galifianakis in a Kanye West video.
David Cross/Janeane Garofalo in Superchunk's Hyper Enough
It's pretty sad the only one I can think of is Jamie-Lynn Sigler in 'Jizz In My Pants'.
ETA Eddie Murphy in 'Remember The Time'
Alicia Silverstone in Aerosmith's 'Cryin',' along with Josh Holloway (aka Sawyer on Lost) appearing at the 3:30 mark: