I like the old actors who basically just played themselves.
I could watch John Wayne, Humphrey Bogart, Peter Sellers, Sean Connery, Patrick McGoohan, or Laurel & Hardy in just about anything they were in.
For true craftsmen, I'd have to go with Sirs Alec Guinness and Laurence Olivier
For actresses, it really varies by movie, although Bette Davis, Olivia DeHavilland, and Hepburn have quite a long list of classics.
For best couple, I have to go with Fred Astaire & Ginger Rogers.