Heler said: PJ is not RJ. RJ is one of the list. Bertram and Kirkland are connected to RJ somehow, but neither of them are RJ. In one ep, Krikland asked Lennon if he remembers him, and then he kills him. This is too obvious and too simple, he cant be RJ. RJ would probably sent someone to kill Lennon (like Kirkland). I mean, kill a man in a hospital ? Isn't it a little too risky for RJ to do it himself ?
Krikland and Bertram had a little odd conversation, so we can tell for sure that both of them are connected to RJ. Now, i think B. Heller wouldn't show us the "puppeting" of RJ. If Bertram really is RJ, B. Heller wouldn't let us suspect him so easy (The conversation with Kirkland, etc).

Reede Smith and Thomas McAllister - deep down, we all know it's not them. : )

Ray Haffner: A member of Visualize. RJ is a really smart man. I don't think he would fall for that sh*t Visualize (new religion and stuff). But, he could use Visualize as a mask, hiding place etc. Even so, he is not a serial killer model. Also, he is too tall :D

Brett Stilles is just too old. But, he is a real mistery in the whole series. Always he shows up in an episode, something strange happens. 

Brett Partridge is just the guy for a cold blooded serial killer. He has that mysterious something in himself. I think he's the one. But it definitely has something to do with Brett Stilles.
BRETT stilles & BRETT partridge :D