I think that Brett Patridge was supposed to be Red John at the beginning of the series, but then the writers introduced a more interesting character in the second season: Bret Stiles.
Just think about it, he has been the most recurrent character of all the seven suspects and he has always been presented as a mysterious man with a great power to influence people (specially woman, like Van Pelt), he has shown a lot of sympathy for Jane and also, Jane has never been able to read him the way he reads other people.
I noticed that when Haffner gave Lisbon the information about Stiles whereabouts, he already knew that Jane was looking for him. So, basically he wanted to be found.
Also, I think that Haffner has been an errand boy for Bret Stiles, acting like Roy Tagliafierro and meeting with many of the people that have been identified as friends of Red John.
Many people don't believe in this because they cling to the clues related to the physical appearance and the age of Red John. I think that the first murder of Red John, and the birth of the happy face happened with Haffner as a disciple of Bret Stiles.
Finally, I want to add something else. Since the beginning of the series, Red John has not shown any rational criteria to select his victims, but if we think of Bret Stiles being him, we could also associate the murders with reasons related to religion and weird beliefs (like thinking that someone is inmoral and doesn't deserve to live). Also it would explain the extreme loyalty of Red John friends.
I just write a summary of some of theories posted here, adding some of my own ideas. Please let me know your opinions! 

I think that Brett Patridge was supposed to be Red John at the beginning of the series, but then the writers introduced a more interesting character in the second season: Bret Stiles.
Just think about it, he has been the most recurrent character of all the seven suspects and he has always been presented as a mysterious man with a great power to influence people (specially woman, like Van Pelt), he has shown a lot of sympathy for Jane and also, Jane has never been able to read him the way he reads other people.
I noticed that when Haffner gave Lisbon the information about Stiles whereabouts, he already knew that Jane was looking for him. So, basically he wanted to be found.
Also, I think that Haffner has been an errand boy for Bret Stiles, acting like Roy Tagliafierro and meeting with many of the people that have been identified as friends of Red John.
Many people don't believe in this because they cling to the clues related to the physical appearance and the age of Red John. I think that the first murder of Red John, and the birth of the happy face happened with Haffner as a disciple of Bret Stiles.
Finally, I want to add something else. Since the beginning of the series, Red John has not shown any rational criteria to select his victims, but if we think of Bret Stiles being him, we could also associate the murders with reasons related to religion and weird beliefs (like thinking that someone is inmoral and doesn't deserve to live). Also it would explain the extreme loyalty of Red John friends.
I just write a summary of some of theories posted here, adding some of my own ideas. Please let me know your opinions! 

Im sure Bret Stiles is RJ.

RJ is the couch carrier. how did he know to stop and hand PJ the coins? why did he hand PJ coins in one of the important parts of the show? why would the writers waste time putting this small scene in if it did not have meaning. we are going to find out this guy has been in several shows thru the years in the background that very few of us noticed. the list of 7 is just fluff so they will have a storyline to continue with once RJ is revealed. they want a next season. this guy was from texas and knew to hand the change to PJ from the couch? he was there only a few seconds and stops and hands it to PJ with all the other people there. im not sure how all the dots connect but if will be fun watching. thanks!

does anyone else think its fishy that a guy carrying a couch in the middle of a very important scene stops to hands Jane some change. how did he know it was Janes? I think we will find that this person (possibly RJ) has been in many shows thru the years in the background. the storyline going im convinced is to hook us into another season. we will learn who RJ is (couch carrier?) im certain. they cant and wont answer all the questions because they want another season. KF and Grace I still think are involved someway. does anybody know how much change he gave him and could it be for a reason? silly to think just some joe finds coins in a couch and automatically knows there Janes. hell he was only there for 10 seconds. look and listen to him! ive seen him before I just know.

The list of RJ suspects :

1. Reed Smith - Judged by Patrick Jane and he believed that he's not Red John.

2. Gale Bertram - He's one of the top member of Tiger Tiger Organisation and he told Patrick Jane many times that he wants to be there when he finds Red John. He's running from everyone, taking his cash and no proper planning. He's not Red John for sure.

Now the remaining 3 suspects presumed to be dead by coroner.

Lisbon found a foot in Jane's house which seems to be either Haffner's or McAllister's.

The writer of the show didn't confirmed that all 3 are dead but he confirmed that there are deaths from the explosion.

The show is made in such a way that no one will accuse Bret Stiles.
He's definitely Red John.

Please comment if you want to say something.

I found something that could explain everything when I mixed every dumb theory.
Bret Stiles gang banged the aunt of Van Pelt, then every spermatozoon fused all their DNA and produced a superpower psychic abandoned to a con father at circus.
But his Evil Plan didn't work and he turned out to be a wonder boy.
Then Bret tried again and Red John was born with a little more consanguine farmboy's sperm.
That could be explain everything :
Red John could be a twin, a father, a son, a daughter, a brother, a sister, all at once, and he can fits every stupid theory you are making.
He can even easily fake his death apparently it's a common thing to do when you are a common smart psychopath.