George Burns was the classic old, old man who came back and stayed back. His big comeback was in “The Sunshine Boys” when Burns was 81, but milked another 20 years out of the old guy leading man/still working when it was uncommon.
Since then, we have William Shatner, Clint Eastwood, Dick Van Dyke, Betty White, and others whom I do not know of who are in their 90s and still getting real work. What’s more, they are doing good work and are still warmly appreciate by both those who have known them from childhood and those who are just seeing them for the first time.
Clint's been in so many films I can't even begin to say which is my favorite. His first appearance, albeit a small one was in Revenge of the Creature in 1955.
Certainly he's a part of life. As long as I've been here Clint Eastwood has been making and staring in movies.