Sheriff McAllister, in his one episode, nearly abducts Van Pelt and seems very threatening and capable of being a serial killer.  If I had time (and knew CA geography better) I would go back and figure out where the Red John murders were in relation to where McAllister is sheriff. 

As for all the discussion of Red John having great contacts and influence, I believe this is a misdirect.  Red John was just a smart serial killer until he killed PJ's family, then be seems to have become more and more influential.  I believe that Brett Stiles is using Red John to get at PJ.  Brett is a great need to control others, and to use them to his own ends.  Ever since PJ came across Brett's path, Brett has desired to control PJ.  Brett is using all his influence, sometimes to Red John's benefit, sometimes to his own benefit, to gain control of PJ.  This is a Moby Dick story where PJ and Brett are both Ahab and the whale.

The other characters who seem to be part of Red John's minion (he is many) are actually being manipulated by Brett either directly or indirectly to serve Brett's purposes directly, and sometimes Red John's indirectly. 

This theory will work with any of the lesser characters being Red John and Brett pulling the strings, so Partridge could also be Red John in this scenario, however, I like picking McAllister because he is the least likely suspect.

I'm not going to hazard a guess, but offer a few points that people may have not thought too deeply about.

Bob Kirkland works for homeland security and, as witnessed in one episode, is in league with Bertram and member/s of the FBI. This leads me to believe that Red John is not just a serial killer, but presents an issue if he is caught by the wrong people, including CBI, and most certainly Jane. Red Johns resources and information also hint that he could have more information that cannot be revealed. I believe Bertram and Kirkland can be ruled out, and are acting as a third investing party for their own ends. Also, there has to be more to Red John knowing Janes happy memory, such as knowing him, or just of him, before the events leading to the start of the show took place. In what capacity I can't be sure, but Heller is very precise in his planning and I don't think these loose ends just happened by chance. I therefore think that season sixes main focus will be on the full backstory of Red Johns connection to Jane, as well as Homeland securities invested interest in him. As Heller said that anyone as Red John is going to be a disappointment I think he plans to offset that by having a great and much deeper backstory to Red John, and his connection to Patrick Jane.

If I was pushed for a guess I would go for Sheriff mcallister. I won't list any evidence to support this, Ii just feel that if he were any of the organisations (visualise/Haffner FBI/Smith CBI/Partridge) subordinates they wouldn't be able to act as freely as they do, and if it were the leader of the organisation (visualise/Styles CBI/Bertam Homeland Security/Kirkland) then it would be too easy to explain away. Also, he is the only one out of the seven that isn't in a high position of power. He is Sheriff, but I don't put that in the same league as the rest.

I can't wait for the amount of butthurt there will be when partridge isn't red john.

The amount of whining will be even greater than when Mashburn wasn't on the
seven suspect list.

I'm surprised not to see more people looking at Alex Jane, Patrick's father. I think there's now an excellent case for considering him.

The show has been very careful to avoid giving definitive clues, and to include a lot of misdirection. Hence we should look for an answer that would provide an elegant conclusion, but that Heller has avoided hinting too directly.

Alex Jane is an obvious choice because of his absence. For someone so important in Patrick's development, he has received almost no coverage in the series, and that cannot be an accident. This absence from the plot is probably the strongest evidence pointing to him: he is being reserved for a future misdirection (which may have already started, in 'Red John's Rules'), or he is Red John himself. 

'Red John's Rules' confirmed that Red John's talents as a mentalist exceed Patrick's - guessing the seven names on his list, orchestrating the event so that Patrick would receive the disk that Lorelei recorded - all impressive feats. (It is, of course, possible that Sean Barlow's comments on John being a psychic are correct - but if you believe that, it takes you down a very different route.)  

It also shows that Red John has intimate knowledge of Patrick's childhood - not just the carnival circuit, but specifically of Patrick's upbringing. This includes information that almost certainly could not be obtained from third-parties - he selected the victim in that episode to make that point to Patrick. 

The seven people themselves are perhaps less compelling on purely dramatic grounds - none would give as satisfying a conclusion as it being Jane's father. A couple of them have solid grounds for suspicion, and Kirkland is at least an accomplice, but it's too obvious. Even the handshake clue may itself be a misdirection - after all, CBS and Heller have no obligation to tell the truth. 

I've enjoyed watching the theories since I discovered the site since the season 5 finale. 

Two things I noticed:

Red John likes to upstage Patrick. Many have pointed out in one episode Jane walks away and then pops back out to scare Brett. Later Red John does the same to Patrick. Then in the season finale Jane catches a "break" and Red John makes it well known that what he did wasn't cleaver, and then Red John goes to prove that he himself is cleaver. This leads me towards Brett, seeing how Patrick has belittled Brett since he first met him. Always undermining him. Even when Patrick came on TV to dismiss Red John which in turn triggered his families murder. Red John has always had to upstage Patrick.

At http://www.youtube.com/watch?feature=player_detailpage&v=sd5glnwOmzw#t=17s you catch a glimpse of Red John. His hands and wrist look to resemble Brett's physique. Although as he walks by, he doesn't appear to be as slender as Brett. Perhaps it is his clothing that skews that. To note though, his hands while holding the cup appear to be a closer match. This scene for me at least rules out Stiles as his hands are much larger. I'll have to look for clips of the others. 

I have two points that came to my mind recently

1) I do not understand the whole "Lorelei and Patrick made the video together" thing... if this was the case (=Lorelei wanting to help PJ instead of seeking revenge alone as we saw in the episode)....
WHY WOULDNT SHE TELL PJ WHO RJ IS DIRECTLY??!


2) Bruno Heller just wrote these episodes. I am pretty sure that Heller wrote the main RJ storyline without leaving the job to his other screenwriters, so we should filter the seven suspects against this episode list. I would dare to add that RJ was introduced in one of these episodes!

·        
Pilot"

·        
"Red Hair and
Silver Tape"

·        
"Red John's Friends"

·        
"Carnelian, Inc."

·        
"Red John's
Footsteps"  

·        
"Redemption"

·        
"Black Gold
and Red Blood"

·        
"Code Red"

·        
"Red Sky in
the Morning"   ·        
"Red Sky at Night"

·        
"Red Moon"

·        
"Strawberries and Cream"   

·        
"Scarlet Ribbons"

·        
"Cheap Burgundy" ·        
"The Crimson
Hat"   ·        
"The Crimson Ticket"

·        
"Red John's
Rules"

Does anyone know if Jane actually saw his wife and daughters body after they were murdered? I just watched the last episode of Elementry, which got me thinking that maybe Red John is actually Janes wife who faked her own death...who else could possibly know Janes 'happy thought' from his childhood? He clearly states he told no one that thought, but does that include his wife? Furthermore, the writers of the show clearly know whoever they pick to be Red John will be a complete let down unless its someone completely out of left field that NO one could have guessed. Has anyone ever stopped and thought about what kind of a woman Janes wife had to be to mentally keep up with him to the point he would commit to marrying her? Red John is just as obessed with Jane as Jane is about Red John...there's a relationship between them. Red John would have killed Jane by now just to make sure Janes doesn't figure out who he/she is, considering Janes smarts combined with his determination to kill Red John. The only way Red John can, with 100% certainty, continually interact with Jane and know he/she won't be caught, is to literally be the only person Jane belivies Red John can't be....his "dead" wife.