i believe walter mashburn is red john. brett partridge seems more like a fanboy, too obvious, and not "mature" enough to be red john. if he were, it would be child's play and not "grown-up" squabble between he and jane. i don't believe the real red john would even mention himself, let alone gloat about red john.

+ mashburn seems split personality. one moment he is enjoying the moment, the next saying something very analytical
+ he and jane get along very well
+ he wore a red turtle neck (which i think was their way of teasing us, whether or not he is red john)
+ he slept with lisbon, which would upset jane because jane is obviously close to her and cares much for her (red john is always looking of ways to torment jane, like kidnapping kristina fry and doing whatever he did to her)
+ red john has to have big time connections and money; walter has both and has admitted he has both (a way to gloat because red john may not be obvious, but it still egotistical)
+ mashburn is bored and will do anything for a thrill, probably even kill
+ when red john saved jane from those kids in the last episode of season 2, he asked him "do you know who i am?" this, to me, indicates that red john has already met jane in person as him real self. anyone he has met before the end of season 2 could be red john. mashburn is in this list, having appeared in season 2, episode 13.
+ red john and mashburn share certain qualities, such as being a womanizer
+ mashburn is very interested in jane, unlike most people who find him annoying, and inquires much about his mental capabilities
+ red john is always one step ahead of people; mashburn was one step ahead of yuri bajoran


when he was trying to blow him up and left the room to "flirt" with lisbon just before the bomb went off
+ jane and mashburn get along like bffs could just like lorelei said he and jane should be bffs from the moment they met
+ jane and mashburn have similar personalities, as do jane and red john
+ mashburn is intrigued at the idea of being a suspect or the killer, a quality that someone who enjoys murder and mystery as much as red john would not be able to hide
+ in mashburn's first episode, i believe he nearly made a slip up when he said he had done a background check on jane and "you lost your wife and kid to a serial killer, your fault...you think;" the change in voice tone from "your fault" to "you think" indicate that he was making a correction, so as not to giveaway that he himself thinks it was jane's fault; this could be because he is red john and leaves responsibility on jane because he wouldn't have killed them had jane not said what he said or it could simply be to not insult jane because he is sympathetic of his loss, though it still remains his fault
+ when talking about how jane manipulates people's minds, he says it in a complimentary way - "you play mind games with people. you size up their weaknesses, and then you give them the rope to hang themselves"
+ mashburn says he "hates being ignored;" obviously when red john feels he is not getting the attention he deserves, he takes it
+ after saying he "hates being ignored," he says he is "cunning, ruthless, and hates to lose;" red john has come to see this squabble between he and jane as a game, a game he is always one step ahead in and always wins; when he doesn't win, he gets very upset and plays hardball
+ red john wants jane to join him last season; why? looking from the perspective of mashburn, he probably wants someone to "play with;" it's no fun alone; a man like mashburn needs not only supporters, but also partners
+ they have made mashburn a very loveable character, much like jane; it would be upsetting for him to turn out to be red john (unlike partridge who is so obviously cold that not many could possibly like him and a lot even suspect him of being red john - red john is not obvious, he himself would be insulted at such a thought)
+ jane is not stupid, but i think they pulled a fast one on us; in jane suspect notebook he flips the page quickly to the next two pages; i think this is because the first two pages has the true red john; mashburn is listed on one of those first two pages
+ when red john makes a physical appearance, he is tall and well masculine built like rigsby or mashburn, unlike partridge; he has young posture, unlike brett stiles
+ in this image: http://images4.wikia.nocookie.net/__cb20110217055161/thementalist/images/0/0e/Computer-reflection.jp...
there is a computer reflection in the 7th image; it is said to be jane in this image, but it is possible it is mashburn, since mashburn and jane has similar features, plus they made it where you cannot see the hair (jane is curly, mashburn is spiky)

just mashburn's personality and behavior alone, i believe, is enough evidence that he is red john. somehow, the smiley face connects to the true red john (whether it be mashburn or someone else). i believe that is the true key to finding out who red john is.

thank you!