Any TV series recommendations?

A lot of good suggestions here.  Absolutely agree with Big Bang Theory.

I've seen people suggest the Shield and Lights Out, a little surprised that I didn't see anyone mention Justified.

And if you want to go back a few years, I would suggest Dead Like Me, Firefly, and of course, Sports Night.

I also think you should probably be looking for shows that are a completed series.  When I’m looking for a new show to watch I would much rather get into a show that is already done and has 7 full seasons to watch than a show that is still running and only has one season under its belt.  

The pilot for Justified was one of the best I’ve ever seen. I, and a lot of people who watched it, thought I was seeing the beginning of a show that would rival The Shield. Unfortunately, it was downhill from there. With the exception of the last few episodes it seemed like each episode was worse than the previous one.  The vast majority of the first season was just a typical cop show with a new bad guy every week and basically no story arc.  

Lost (6 seasons, hooks you in from the first scene, somewhat disappointing finale but open to interpretation)

Leverage (2 seasons on Netflix, amusing, couple hot chicks)

Walking Dead was good at the start as StraightShooter said but it did slow down, more about the character development so far rather than just zombies chasing people.  Only 6 episodes in the first season, hopefully the next season has more.

Rome (HBO, 2 seasons.  Good first season, second was kind of weak) 

Eastbound and Down people either love or hate.  I loved it personally.  McBride is great and the secondary roles are hilarious.  Stevie Janowsky is the best.

That’s also a good one. I really wish they would have given it one more season though.