Rachel Mason.
I always rooted for her, and there's something very watchable about Eva Pope in anything she's in. She's just very... what's the word... intriguing. The relationship with Eddie was great, although I hated the Melissa storyline. Her opening storyline, when she revealed to be an ex-prostitute, was one of the show's finest moments for me. Her feud with Max made me love her more.
I also loved Steph and Grantly. Old school.