|Rhapsody in Blue (1945) [George Gershwin]: Dies (off-screen) of a brain tumor; we learn of his death when the news is announced during a concert. (Thanks to Bryan)
Cleopatra's Daughter (Il Sepolcro dei re) (1960) [Inuni]: Suffocated/buried alive when he is trapped in the tomb after helping Ettore Manni and Debra Paget to escape.
Quincy, M.E.: Hot Ice, Cold Hearts (1977) [Professor Wren]: Injected with stonefish venom by Andrew Prine while Robert is scuba diving; he dies shortly after Jack Klugman and Lynette Mettey help him back onto the boat.