Damn it, Sofa King, you’re right. John Huston was the VOICE OF GOD in “The Bible.”
Let’s not forget Frncois Truffaut as Lacombe in Close Encounters!
And Stallone has a cameo in the horrific sequel to Saturday Night Fever, “Staying Alive”.
Director David Cronenberg (Rabid, The Brood, The Dead Zone, The Fly and a great many others) has appeared in cameo roles and bigger roles in his own films (an obstetrician in The Fly) and in those of other directors (playing serial killer Decker in Clive Barker’s NightBreed). See his page at the IMDB:
http://us.imdb.com/Name?Cronenberg,+David
John Sayles, who writes and directs an awful lot of his movies, has been known to write himself a dandy little part. Beginning with Return of the Secaucus Seven, through Lianna, Brother From Another Planet, Matewan, Eight Men Out, City of Hope, and Passion Fish, Sayles wrote himself in.
He’s also had cameos in a ton of films he didn’t write or direct.
Rob Cohen plays a pizza delivery man in The Fast and The Furious (and yes, the movie sucks).
Do Quentin Tarantino and Kevin Smith count or are their roles too big?
Frank Oz has appeared in a bunch of John Landis films.