C.J. Cregg, in The West Wing. Generally speaking, I love the female characters in The West Wing: they're strong, sensitive, funny and hold their grounds (the only one I couldn't really get used to was Amy Gardner): whether it's Abbey, Mrs Landingham, Joey Lucas, Ainsley Haines... I have to say that Aaron Sorkin knows how to write great female characters! And now, a few C.J. moments (at least the ones I haven't already linked to in the past few days – you'll find the root canal and the secret plan to fight inflation there ).
First of all, the Jackal. There is no way I can talk about The West Wing and C.J. in particular without linking to The Jackal!