The Sopranos
The West Wing
The Wire
The Shield
Oz
Deadwood
Battlestar Galactica
Friday Night Lights
Breaking Bad
Mad Men
24 (Season 1, more if you want)
Lost (Season 1, more if you want)
Serenity
Game of Thrones
I've enjoyed The Big C recently. First and second series were excellent, third still good and the fourth changed to being just four hour-long episodes and had a bit of a sense of just wrapping things up but it was still very watchable. Excellent cast all round.
And I got very fond of the Mentalist last year, too.