The way he shut down a reporter who wouldn't stop hassling him about his being cast as Batman.
Keaton: I don't get the importance. I was doing an interview, and the guy was going on and on about it, and finally I said, "Did you read the paper this morning?" And I wasn't being a smart ass, I was just being real. And he goes, he just said yes or no, I don't know. I said, "Do you know there are bodies literally, literally like a logjam floating down rivers in Rwanda right now from being hacked up and killed — right now?" and he goes, "Oh, that's terrible … " And I'm like, "Who gives a fuck who's going to be Batman?"
The fact that Barack Obama is a fan of his (he greeted Keaton with "Why don't you make more movies?!").
His Hidden Depths moments on the main page, especially where he says that he didn't care about preserving his status, he didn't want to be pigeonholed or typecast, he just wants to do what he loves (even if that means he never gets to be the "current groovy guy").
His performance in Kenneth Branagh's Much Ado About Nothing. He was very doubtful about doing Shakespeare and was sick as a dog for the whole shoot, but ended up being just about everyone's favorite part of the film.