If you're looking for sci-fi shows, I would highly recommend all of these:
The X Files
Two FBI agents, Fox Mulder the believer and Dana Scully the skeptic, investigate the strange and unexplained while hidden forces work to impede their efforts.
(My all-time favorite show.)
Fringe
A television drama centered around a female FBI agent who is forced to work with an institutionalized scientist in order to rationalize a brewing storm of unexplained phenomena. (Sort of like a modern X Files with less focus on aliens.)
Lost
The survivors of a plane crash are forced to work together in order to survive on a seemingly deserted tropical island. (Don't let the description fool you, there's plenty of sci-fi elements.)
Eureka
The best minds in the US are tucked away in a remote town where they build futuristic inventions for the government's benefit. (This one can be cheesy, but still good.)
Warehouse 13
After saving the life of the President in Washington D.C., a pair of U.S Secret Service agents are whisked away to a covert location in South Dakota that houses supernatural objects. Their new assignment: retrieve any lost objects and investigate reports of new ones. (Also cheesy at times but still intriguing.)