As a guy who grew up on Role Playing Games (RPGs) I am a big fan of spending experience points. Basically, for all of you who had better things to do in your teen years, a character in a RPG would get experience points for doing stuff and then you, the player, could spend those points to make your character faster, stronger, or able to speak French. I honestly believe that it was the hard work that went into gaining experience for my character that gave me serious respect for a good character arc in a story. One of my favourite characters which show this phenomenon in genre fiction is Anton Gorodetsky.
Anton is the protagonist in Russian author Sergei Lukyanenko's Night Watch, series of books. Basically he is a lower level wizard (tech support, really) in Moscow's Night Watch, an organization which guards the city from the members of the Day Watch, who claim they do the same thing - the series has a real Russian Cold War feel to it. Anyway, in the first novel Anton is given his first field assignment, to track down a vampire and of course it all goes horribly wrong - otherwise there wouldn't be much of a story.
Throughout the four novels that comprise the series, Anton grows in his abilities, meets a girl, marries her, is promoted, becomes a dad and eventually goes much farther both professionally and personally than he ever imagined. I love when this happens to characters in genre fiction. Rather than simply solve the problem, move on and repeat, Anton learns from each major event in his life, which causes him to grow as a person. I find that far too often, the characters in genre fiction simply don't change from one book to the other, the same awesome guy shows up, kicks ass, and leaves. Character growth is good - it is what keeps me coming back for more.
*One quick note about the movies - I had already read the books when I saw Night Watch, and I really liked the movie. I have been told that if you haven't read the books, the movies don't make much sense. I will say this though, Konstantin Khabenskiy (pictured above), who plays Anton in the films is really, really good. I totally bought him as the character and that's pretty tricky when the character in the novels is such a favourite.