With Charlie given the news by Desmond that he has to die in order for the rest of them on the Island to be rescued, especially that of Claire and Aaron, this sets him off on a contemplative journey as he revisits the 5 greatest moments of his life. We all know what his eventual #1 pick would be because he is willing to sacrifice his life for Claire and Aaron. It's a very deep and profound moment, not just for the character, but for the series as a whole. When you have such incredibly selfish characters like Locke and Ben, it's very refreshing to see someone give so willingly for another and not ask for anything in return. I know I bashed Charlie a lot during the first couple of seasons and rightfully so. He was after all one of those selfish types and the fact that he was on drugs didn't help his case either. Charlie will get to shine in the final episodes for this season and go out on his terms.