Patrick Jane
While many in the Blogosphere are distracted by the direct naming of 7(Now 6) Red John suspects, most now seem to be shying away from the possibility of a killer outside the obvious. I believe that the creators of the show are drawing attention away from the answer like a pickpocket does an unsuspecting mark. The art of misdirection has been used in shows for quite some time, now the mentalist is planning to follow suit. While the current episodes blow a screen of smoke, flashing red herrings for each listed suspects, Patrick continues to stay one step behind Red John. At one point in the latest episode, Teresa mentions that it's "like he pulled it out of your head." Maybe the famous mentalist is fighting a battle against himself, which would explain why no one can catch the elusive criminal. I also believe that before Jane began killing, Brett Styles was a earlier version of Red John (which would explain the episode red barn) and somehow passed the duty down to Jane. Jane may be taking the persona Red John to new extremes which would explain his conflict with styles. And that, is my two cents on the matter.