I would need to include Vic Morrow as Sgt. Chip Saunders and no list of characters could ever be complete without honorable mention of Richard Jaeckel as Everyman because he was in every movie and TV show that was ever made from the time of his seventeenth birthday until the day he died.
How about the guy who played Gus the Firmean on "Leave it to Beaver"? Great character actor. I have to find his name on IMDB.com... and the answer is.... wow, Burt Mustin born in 1882 and died in 1977.