Lots of good suggestions already. Not long finished 'Galactica' (the reboot, obviously)- instant classic.
If you don't mind subtitles, the brilliant French series 'Spiral' (first two seasons on DVD now- £16 at play.com!-, third will be on BBC4 soon)- if you like 'The Shield' and 'The Wire' (and I most emphatically do) this will be right up your street. And if you haven't got into it already, 'The Killing'. Which will also be out on DVD soon. And if you've never seen it, the mini-series version of 'Das Boot'.
'Seinfeld'
'The Prisoner'
and I must remember to buy this myself- the cruelly cancelled after six episodes but utterly hilarious 'Police Squad'.