Ok, so admitidly all of the suspects have majory creepiness levels, but being a creep does'nt necesserily mean your a serial killer. So who is Red John? I think Bertram is the Best candidate. Not only is he strange but he is also connected, a member of Tyger Tyger and (due to his possition) able to keep an eye on Jane and the Red John investigation. He also told Jane that he would be there when Jane caught Red John and low and behold when Jane shot and killed "Red John" who was there? None other then Gale Bertram.

P.S Bertram is great at whistling.
P.P.S Cant wait to find out!!!
P.P.P.S People who say that Red John is Lisbon, Van Pelt, Summer or JANE are either crazy or stupid!