Falling Skies - Action/Sci-Fi/Thriller (Not the best Sci-Fi out there but definately worth a watch.)
Game of Thrones - Adventure/Drama/Fantasy (Amazing. Watch it NOW!)
Justified - Action/Crime/Drama (Something different, worth a watch.)
Spartacus: Blood and Sand, Gods of the Arena, Vengeance, War of the Damned - Action/Adventure/Biography (Really good, definately watch these.)
Vikings - Action/Drama/History (Looking good so far, watch it!)
Some of these shows are for mature audiences only, the Spartacus shows most certainly.