As a bit of an angle on the "TV" show thread, I'd ask who is your favourite film / TV Actor / Actress and why?.
For me it's Gene Hackman, he's versatile and is just so strong in some of his roles, noteably in "Unforgiven" where I thought he played an equivalent lead. I also enjoyed his comedic performance in "Get Shorty" and his character in "Enemy of the State". Although I don't deliberately go out of my way to see him in a film, I tend to rest assured that anything he is in is actually going to be half decent.
My favourite Actress is Helen Mirren, simply for her performance on the UK TV show "Prime Suspect".
I'm pretty undecided on "TV" actors. Bernard Hill in "Boys from the Blackstuff" (UK TV series about the state of the UK in the 80's) still sticks in my mind as an epic and powerful performance, but anything he does from there on in will always be compared to it. Truthfully, there are far too many for me to pick one out.