Originally Posted by
Alen
Assuming you want stuff that's "complete" or has ended, here are a few recommendations:
Arrested development
> awesome fun, I had an unbelivably fun time watching it
Party Down
> another great comedy
Freaks and Geeks
> bit older show, most people don't like it nowadays (it's _old_). I didn't mind watching it, found it interesting and fun.
Twin Peaks
> again a bit older show, but very goddamn good. A bit eccentric and hard to swallow if you prefer superficial stuff.
Firefly
> love/hate kinda thing, it's a space western. Personally I loved it and wish it weren't cancelled. It has some sort of continuation/conclusion movie called Serenity, which wasn't well accepted (it does requires you to watch Firefly first, something most people didn't really do)
Dollhouse
> from the same guy that created Firefly and it's a love/hate thing again. Sci-fi brainwashing stuff, worth watching if you can't find anything better. Some parts are good, some aren't.
Misfits
> still ongoing, but the first seasons work as a complete whole, awesome fun but a bit weird and distinctly teen/brit kinda thing
Carnivŕle
> again, something of a love/hate thing, it's historical sci-fi that had a pretty good start but gradually declined towards the end
Band of Brothers
Pacific
> two shows (related to each other) about a company of soldiers in WWII
Rome
> who doesn't love Romans? Awesome show and everyone loved it, a movie was planned but no clue what happened
Spaced
> Simon Pegg and Edgar Wright. Need I say more?
Sherlock
> still going on, BUT WTFBBQAWESOME
As an added bonus:
Death Note
> awesome manga/anime, definitely worth reading/watching, even if you're not a cartoon/anime fan. Trust me.
Added bonus #2:
Tinker Tailor Soldier Spy
> if you've seen the current movie, this is also an original series (pretty damn old). Interseting to watch from today's perspective.
That's off the top of my head, though there def are more out there.