Daniel Niven - 1967
1967's original Casino Royale starred David Niven, and the result was a weird and wacky Bond-parody. The film was poorly received, whether the satire was intentional or not. Author Ian Fleming did agree, though, that Niven was the perfect actor to portray his vision of James Bond.
Bob Simmons, 1962-1964
Bob Simmons starred in the same Bond films as Sean Connery. He was Connery's stunt double. Remember that iconic gun-barrel sequence? That was not Connery. Even though he didn't play 007 in an official sense, he still counts as one of the many men who have portrayed him.