Most of these have been mentioned but some of my current(ish) faves..

Game of Thrones
Spartacus - halfway through this atm, much better than i expected, loving it.
Boardwalk Empire - if you like Sopranos/SoA you will like this
Walking Dead - latest epi was lame
Dexter
Breaking Bad

Some older classics

Sopranos
Battlestar Galactica
Sherlock mini series was good
Firefly - one of my faves

I like a lot of UK comedies (too many to list) and a few US ones too, like Curb Your Enthusiasm, Eastbound & Down, Trailer Park Boys (Canadian).

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Ben
MY12 WRX Hatch