So we know a few things about Red John.

1) According to one thing I read, it won't be until November 24th that we actually know the name of the real RJ.

2) RJ was "young" back in 1988.

3) He at least had a full head of hair.

4) He's 5'11"

5) Muscular build.

6) Left Handed

7) Afraid of something

8) Fans will be disappointed by who he is.

9) Can whistle.

So here is why I think it is McCalister:

1) His character's stated age is younger than the actor who plays him which I find odd.  He is listed as being born in 62 or 63.  That would make him 25 or 26 in 1988 ... young enough to be the guy.

2) Right height, build, handedness, whistler.

3) He was introduced the earliest of all of the suspects on the list (season 1, ep 2). Given that RJ was the focus from early on (at least PJ's motivation), it seems likely he would be a character since early on.

4) Only one of the suspects who seems to surprise PJ.

5) Straight hair even if it has thinned out lately.

I had previously thought it might be Smith, but McAllister makes more sense.

YES, EVERYONE IS AWARE. WE HAVE ALL WATCHED THE EPISODES. IF SHERIFF McAllister is LEFT HANDED THEN WHY DID HE SHOOT THE GUY ON THE ROOF WITH HIS RIGHT HAND DUMMY? THESE EMIPODES STINK! I USED TO LIKE THIS SHOW, BUT ITS GOING OUT VERY BADLY. NOT A GOOD WAY FOR THE FINAL SEASON TO END!

Are you guys aware that Sheriff McAllister´s first appearance was during the second episode of the first season and he returned just now as a rj suspect? 

When Sheriff McAllister saves Patrick on the roof (Season 6 Episode 3), he helps him up with his left hand, indicating that he is left handed. When Red John is choking Kira Tinsley, he uses his left hand, indicating that he, also is left handed.

10% of people are left handed
There are 5 suspects remaining on the list

Do the maths for yourselves. Thomas McAllister is Red John :D

My evidence is this:

Anagram:

TygerTygerThomasMcAllister

I am the scraggly ratty molester

McAllister in the wedding episode pretended to be afraid of heights to play with Jane. Only RJ would know that info and that Jane would be looking for that.

McAllister was two steps ahead of Jane in the end, he was there waiting for Jane and his captor. Only Red John has demonstrated the ability to anticipate Janes' moves and their results before Jane does.

Its him.

Why would CBI and FBI talk strategy with a smalltime sheriff? Both Reede and Bertram vie for McAllisters attention like children...

Sheriff Mcallister is Red John.

I support my theory on the following facts.

1- In the scene where she saves him and recited the poem Tyger, Tyger: approaches him quietly, without noticing Patrick.

http://www.youtube.com/watch?v=MKZvmwU1ufg

2.- Also goes to him quietly, in the 6x02 which saves him a second time, without noticing on two occasions.

3- In this chapter, we show that cross quiet until the pigeons appears.

4. - On the other hand, the actor who will make Red John, in chapter 8, he looks like him young.

5. - After reading the theory on a Blake poem and see the description http://www.whoisredjohn.com/See-a-theory-Red-John/7453 I am convinced: Old John with white hair

6. - Sherif is connected to Bret Stiles may be his brother or Partridge, in which case the 666 make sense.

7. - The three dots SPOILER Also can carry religious meaning, Representing the holy trinity.

8.- finally when when he killed a accolite in CBI offices he looks dress as a sheriff.

9.- When the list is given the only person who is not called for his name is sheriff