Not "really" famous, but there was one a while ago that saved his owners from a fire.
He was a house rabbit and when the house caught fire, he went nuts and started scrabbling on the doors and woke the family up.
There was another who saved her owner when he slipped into a diabetic coma, she jumped on him and was scrabbling and digging which was very out of character for her, which drew the chap's wife's attention, and she was able to get him to hospital in time