Most people are saying what their favorite tank is, or what they think the strongest is - not many are answering the actual question: what tank is the easiest?
Answer: the absolute easiest tank to pick up and play assuming you have no experience whatsoever is most likely Prot Warrior, as with the right talents all you do is hit Charge, Shield Slam, Thunderclap, Shield Block and Ignore Pain, with the occasional Revenge if you feel like it. Very simple and straight forward if that's what you're looking for.