Addison Montgomery/Kate Walsh
When we first met Addison she was simply McDreamy's wife. Now we were all shocked by this revelation, and at first couldn't help but resent her for becoming between Meredith and Derek. But after a while, she settled in and began making friends, and she became more and more likeable. By the middle of the second series she was a firm favourite of mine. She has this aura about her, she strong an independent, she knows what she wants and isn't afraid to fight for it. However your repeatedly get a glimpse at her more vulnerable side, especially during the course of Private Practice. Away from the staff at Seattle Grace and in a new surrounding you really get to see a whole new side to Addison, she more relaxed and happier which mean we get to see more of her killer smile.