Kaeyoss made a post in the pretty floral bonnet thread in which he mentioned that Michael Carpenter (of the Dresden Files series) was essentially exactly what a paladin should be. I agree, and in fact used him as the basis for a character of mine (family man paladin of Iomedae). Often when pushed into a moral quandry as that character I would stop to ask myself "What would Michael Carpenter do?" And found the results to be quite likely the best paladin action. So what about you gamers? What character out there defines a class/character/role/attitude for you. Who's the character who makea you think "What would ___ do?"
Conan = Barbarian. (Just getting the obvious out of the way.)
Other than the Paladin though, I don't think you can pin down a class to a single character comparison. Maybe an individual character, but not a class. The Paladin class is the only one that comes with strict rules on what is acceptable behavior.
I can't say that I've ever used this method myself, so I have nothing more meaningful to contribute. :(