I love characters that evolve realistically, over time, from people who are less-than-admirable – cowardly, timid, pompous-but-secretly insecure, etc. – into someone strong, resilient, and willing to kick ass and take names. Examples: Wesley Wyndam-Pryce from Buffy the Vampire Slayer/Angel the Series; Dr. Gaius Baltar from Battlestar Galactica (the 2003 reboot, not the original); and to a lesser extent, Dr. Rodney McKay from Stargate: Atlantis... by "lesser extent," I mean that he wasn't quite as immediately unlikable as the other two. They became three of my favorite TV characters.