OK so, not completely convinced Red John is Ron, but I am convinced it isn't anyone involved in "Tyger Tyger" .. I do however think Red John has something to do with the Tyger Tyger group.  The William Blake poem, The Tyger, is first quoted by Red John, so the
claim that he has nothing to do with it cannot be true. I believe Red
John is the "Tyger" to Patricks "Lamb" ("Did he who made the Lamb make
thee?")
I am convinced, based on religious imagery in the show, that Red John sees himself as Satan, or Satan- like figure. This is reenforced by the recurring references to William Blake, and why the next episode is called "The Great Red Dragon." (also when TL enters the house where BP is killed, 666 and a pentagram can be seen on the wall) Other religious symbolism throughout the show lends credence to the theory as well. Lorelei Martin, for example, seduces and tempts PJ with money, security, etc on behalf of RJ in exchange for the head of Theresa Lisbon, a little like Eve and/or Salome.

I think its likely that RJ possesses the same talents that PJ does for hypnotism and suggestion, and uses this to control certain members of the police and others (the "Tyger, Tyger" group etc).  He may see himself as a Satan commanding his own group of fallen angels. The police that are not involved, or the innocent members of Patricks team can be seen as the "good" angels in that analogy. (Interesting to note here that Patrick's wife's name was Angela).

Why Ron though? I think he makes sense, he has been present since the first season, he definitely has given himself a Satan-like haircut. He does clerical work, which is something PJ said of RJ in an extra scene of the pilot episode. He is involved with the CBI so that he can keep an eye on the progression of the case, as well as surround himself with death etc, but does not have an active roll in solving the cases. I like the idea of him being the "Where's Waldo" character that everyone mentions, and I like that his name is close to "Red John". We know that RJ likes to keep his alias' similar. He matches Rosalind Harker's description, and does not go against the rough picture we get from Sophie Miller.

A few problems with Ron as a candidate: I am a little troubled that the character hasn't been given a last name, perhaps he is too small of a character to be a good choice for Red John and that Rosalind did not mention that RJ had facial hair.

does anybody else feel like they left out alot of the story of bob kirkland twin brother?  the way he said he just disappear and was never found again and that he just thinks red john didnt seem like good enough reason to go around killing everybody
i think is possible bob kirkland twin brother is actually red john unless is already confirmed that one of those 5 suspects is, just my thoughts

Recently, I have been 95% sure that RJ is Haffner and equally sure that he isn't Stiles. Episode 6 make me think opposite, haffners behaviour with Lisbon in the cafe made me think he's definitely not RJ, far too weak. Stiles pairing the 'clown' face on the woman at the ritual made me think it had to be him.

Then, when the other three suspects had the tattoos, I ended the episode thinking it must be one of them. However it doesn't really add up having one of these three as RJ. Sure, they're all portrayed to be creepy and sinister..but why would they need to send a PI to infiltrate Cho et al, when they could just big lisbons office, having inside access and all. It would seem to me that these three suspects are together, bound together by something due to their meet ups etc, but that none of them really fit Rosalind's description or have RJs intelligence levels.

Let's not forget that during these 'reveal' sessions the PJ stages, he is usually a few steps ahead of the pack, including us. I think he knows the three suspects he ordered to stand up are not RJ, and that's why he seperated them from the group. He probably wanted to give stiles and Haffner false confidence that Jane is not on their trail.

The explosion: let's not forget that jane used to perform trickery. Could the explosion be a diversion or something jane put in place to seperate everybody, disappear with brett and Haffner?

Look at Brett stiles , so nurturing towards janes investigating. Almost fatherly, he acts as janes mentor, kindly pointing out to him with interest that Bertram & FBI guy had the tattoos too. Perhaps him and stiles have a connection that jane is not aware of? Haffner carries out the acts of RJ , unbeknownst to father figure stiles..he's doing it for recognition/attention from stiles.

The visualize connection is just too strong!!!

The sheriff is one crazy fella. He hid the bomb under his hat.

I knew he was the one coming up with this explosive plan when he smiled after PJ told them to move to the other corner.

Both Bertram and Smith were kinda worried but the sheriff, nope, he just keeps on rocking his hillbilly attitude and shrugs it off like a boss. 

PS: I want to note that just after Patrick calls the sheriff to set the meeting, Bret Stiles receives a note "Patrick Jane is looking for you". If we assume that RJ and Bret are related somehow (blood? friendship? idk), maybe RJ isn't *that* evil after all....he cares for his beloved mentor (father perhaps?).