The Execution of Private Slovik - Martin Sheen

  Ocean's Eleven - I'm not sure which role he was offered

  Breakfast at Tiffany's - He was unable to accept due to contractual obligations to the series Wanted: Dead or Alive.  George Peppard  eventually got the role.

  Marooned - Gregory Peck

  King Rat - George Segal

  Return of the Seven - Robert Fuller

  The Kremlin Letter - Richard Boone

  Ice Station Zebra - Rock Hudson

  Butch Cassidy and the Sundance Kid - Robert Redford

  Dirty Harry - Clint Eastwood

  Play Misty for Me - Clint Eastwood

  The French Connection - Gene Hackman

  Fort Apache, The Bronx - Paul Newman

  The Betsy - Robert Duvall

  First Blood - Sylvester Stallone

  One Flew Over the Cuckoo's Nest - Jack Nicholson

  Apocalypse Now - Martin Sheen

  Raid on Entebbe - Peter Finch

  Raise the Titanic! - Jason Robards

  A Bridge Too Far - Robert Redford

  Grace Quigley - Nick Nolte

  The Missouri Breaks - Jack Nicholson

  The Towering Inferno II

  Close Encounters of the Third Kind - Richard Dreyfus

  The Driver - Ryan O'Neal

  Convoy - Kris Kristofferson

*There are several other films he did not turn down and may have made had he not fallen ill including The Bodyguard, Dogs of War, Quigley, Down Under, Hang Tough and Pale Blue Ribbon.