If there's one thing I've learned about this show from watching six years, it's that there were always logical and interesting reason as to who the killer is in each episode.  Take a look at episode five of this year, "The Red Tattoo".  That episode had a truly unique and very cool answer for who killed who, and in the end, the answer was very logical.  The answer to who Red John is would also be very logical.

Based on six years of Red John evidence, who is the most logical choice for Red John?  I vote the Sheriff for the following reasons.

1.)  The Hunter Ethos:  The Sheriff loves to hunt, loves to kill.  We all know Red John loves to kill...

2.)  Mobility:  Most of the suspects are pretty confined by their jobs, but a Sheriff in wine country has much more freedom.  They spend many hours alone with no one around.  Plenty of chances to commit murders.

3.)  Unsuspecting:  No one ever thinks a Sheriff's vehicle might contain a serial killer.

4.)  Location, location, location:  There's not much out in Napa Valley wine country, and that's the point.  It's out of the way and a great place to hide.

5,)  The Profile:  He fits the profile to a tee except for his hair.  For that there's a simple explanation.  He lost it over the past six years.  I know for a fact that the actor, Xander Berkeley had much more hair six years ago when he was cast.  I've seen pictures of him on Nikita and he still had enough hair to be defined as short and straight.

6.)  Tiger, Tiger:  Of the three suspects with a tattoo, the Sheriff seems an odd choice to be a member of "Tiger, Tiger".  He doesn't really bring anything to the table.  He has very little jurisdictional prowess.  However, if you are Red John, you wouldn't want a job that is high profile.  You would prefer to stay in the shadows and rather have your friends be powerful. 

7.)  Ornithophobia:  Although Sophie Miller thought Jay Roth lied about the kind of phobia, she believed he did have an actual phobia.  The Sheriff has a fear of birds.  One flew by him in the Church in episode 3.  He panicked and stated, "Didn't see that coming!  I hate those things!"

8.)  He Is Mar/ked:  We knew Renfrew tried to write something on his bathroom wall when he was dying.  He Is Mar could easily be He Is Marked.  It would definitely confirm that Red John is one of the three with a tattoo.

9.)  Process of Elimination:  None of the other suspects fits the evidence properly save for Ray Haffner, and he does not have the tattoo.

10.)  I'll call you "Tom" then:  RJ usually kills anyone who poses a threat to him, but not Patrick Jane.  He likes him too much.  He has tried to befriend him with Lorelei and refused to kill him when the 7 suspects were revealed.  Who is the only suspect who really appears to like Jane?  Sheriff "Tom" McAllister.  AND he always calls Jane by his first name, Patrick!