It couldn't be anyone other than Haffner. I'll explain, the bold parts are my reasoning why i feel it's relevant/why i think he's RJ. Normal text covers the facts.
Let's begin with his career background. We know he was part of an FBI unit that dealt with surveillance, until he transferred to CBI, where he was briefly agent in charge (a male Lisbon). This is relevant considering 6:01, which dealt with wiretaps on the RJ suspects. As an expert in surveillance, he would have known that his phone was being monitored, and he would be skilled enough to manipulate the situation to his own needs.
Whilst team leader, he was manipulated by Jane, yet was aware of it (others aren't so sharp), whilst at the same time manipulating Cho into working for him. Jane still prevails and makes him look foolish. He could have easily played the fool, the fact he was aware he was being played shows intelligence that others haven't displayed. By allowing Jane to play him, he played Jane, by hiding in front of Jane's very eyes. His manipulating of Cho showed a darker side, and a ruthless streak.
He leaves CBI to form his own independant company (that is bankrolled by Visualize). He tries to recruit Lisbon. His attempts to recruit Lisbon show that he understands what is important to Jane, he was probably just gauging Lisbon's feelings towards Jane, thinking a few moves ahead, how he could try and drive a wedge between Lisbon and Jane professionally.
He is a member of Visualize. RJ is a visualize member, it's the only way Bret Stiles could know so much about him.
He was at the Farm in 1988. He didn't expect to get found out here. He looks shocked when Lisbon reveals that she knows. He tried to palm blame for the 3 murders onto the girl, when she was only guilty of 1 count of manslaughter.
He shook hands with Jane. Self explanatory.
He played college football, likely for Alabama Crimson Tide Crimson = red.
He is around 6ft tall, medium build, with short/medium hair. He perfectly fits Rosalind Harker's physical description of Roy Tagliaferro
He is one of the remaining 6 Of the remaining 6, only he and Robert Kirkland really match the description, but why would Kirkland break into Jane's room for RJ info if he was RJ, which again leaves the finger pointing at Haffner.
He had discipline problems as a youth One of them likely being anger issues, leading to murderous impulses.
