My favorite TV Detective? That's easy, it's the Dark Knight Detective himself; Batman!
Of course there are others I like as well.
I used to love watching Columbo as a kid. It was a different kind of mystery series as they would show you the murder up front, pre loading you with all the details of the crime and then the "mystery" becomes how the detective is going to figure out the clues. The character of Columbo, as a super intelligent, hyper observant mind hiding behind an aloof, bumbling persona, was always interesting to me. I firmly believe that this was an inspiration to the creators of the TV series Psych. The Shawn Spenser character is like Columbo turned up to an 11!