Walter Mashburn
It is actually too funny. I remember the day when I saw Walter Mashburn  for the first time, I thought this guy has resources and loves the thrill of a crime scene he gives Patrick Jane a beautiful car he has to be Red John. And then I typed the name Walter Mashburn in google and I was shocked by the google suggestion that I thought I saw one of the biggest spoilers in my life... Mashburn is Red John. And I needed to see the remaining season, because the season was already ended. Gladly it was not the case and Red John was still a mystery.

Ray Haffner
After a while Mashburn just disappeared, the only time we could see his name on the little notebook of Jane who is suspected to be RJ. And then a guy named Ray Haffner got a lot of screen time with some very good characteristics. He is like Patrick Jane's rival in looks and brains. Somehow he gets really insecure when he talks to Teresa or sees a spider, so there is a human side hidden in him. It's just like he is supposed to be Red John.

Brett Stiles
He helped Patrick a lot, he helped Lorelei escape. But just one thing bothers me, when he talks to Jane he really talks about Red John as a third person. It could be him, but I will talk about that later :P..

The Sheriff McAllister(reminds me of Home Alone 1 and 2 lol)
I really like this character. He just loves to hunt and it is like he is really intelligent you can see it in some scenes but he just tries to hide it by acting ignorant. I have read many books and it is always quite scary when a Sheriff of a little town has a secret agenda. It's like a big home where he can be himself and relax. And the actor who plays the Sheriff is just awesome, just try to look whenever McAllister squints his eyes it's like that little bit of Red John that you'll see once in a few times. In episode 3 you saw the Sheriff challenging Patrick Jane about the crime scene, it was like a mini game they loved to play together.

Whoisredjohn.com
This is the funny part. The people on this site always figure out to amaze me,  The theories I've read are really thoroughly written. If you're a neutral person you would really believe that all the seven persons are in fact Red John. Somehow I honestly believe that Heller is sometimes looking on this site to see how his viewers are thinking. Maybe someone even got the whole Red John part right. 

Bertram
That Bertram though lol it's like he has a fetish to see how Patrick discovers Red John, every time those eyes and smile are creepy. When Patrick saw those three dots Bertram was like evil o.O Reede Smith was grumpy like always and Thomas was Patrick it's not what you think.

I had an idea, if Patrick somehow already knows who Red John is then we should look at his body language in front of those people where his confidence will lower significantly.

There is still that one riddle that won't slip my mind. When Kirkland brought three coffee mugs, he somehow expected a third person. Who would that be? *suspense sound....*

We should respect Heller for the fact that already two suspects are dead. Don't make yourself disappointed if you want a  dead person to be Red John. Let's just see what the next episode will bring us. With every episode the majority change their opinion who Red John is, no wonder that is the intention of the writes.

Just enjoy, be patient they are all good characters to be Red John,. *cough* not Reede Smith  *cough* 
I do hope it's Ray or the Sheriff, it doesn't matter who it is. I just want to see an episode through their eyes. To see Red John being Red John.