People were actually surprised that Itachi was 'innocent'? I find that shocking. I thought he had ulterior motives all along...right up until the battle where he started talking about the Mangekyo and went seemlingly batshit.
For me, the most interesting would probably be Naruto - a guy who never gives up, even though it is a common theme, I think it's done pretty well in this series. I kind of think Shikamaru and Rock Lee are inspiring too.
The least interesting characters are probably Nagato and Sasuke, if you ask me. They are just walking plot handles with motives that don't make any sense no matter how you look at them.