[Boromir88]

Well, from the way this thread has been set up by lmp (and I guess it was intentional ) is that there is no "correct" answer. All of them really are good choices. In fact, I think the list should be expanded...what about Gandalf and/or Aragorn who were great deceivers themselves! Making Sauron believe they were going to use the Ring to overthrow him, but instead sneak in 2 little hobbits to destroy it. Talk about deception!

Anyway as far as my vote for Saruman. To add onto some of the points...sure you can question parts of Tolkien's letters. But the specific part, from Letter 210, Raynor uses I think fits perfectly in line with LOTR.

Saruman's voice was not hypnotic but persuasive. Those who listened to him were not in danger of falling into a trance, but of agreeing with his arguments, while fully awake. It was always open to one to reject, by free will and reason, both his voice while speaking and its after-impressions. Saruman corrupted the reasoning powers.

If we look at Saruman being able to completely fool Radagast and have Gandalf 'blinded' up until Saruman imprisons him; that is quite impressive. Sure, it's mentioned Gandalf was having some wariness as far as what Saruman was up to, but it's clear Gandalf still trusted Saruman up until his imprisonment:

"At first I feared, as Saruman no doubt intended, that Radagast had also fallen. Yet I had caught no hint of anything wrong in his voice or in his eye at our meeting. If I had, I should never have gone to Isengard, or I should have gone more warily. So Saruman guessed, and he had concealed his mind and deceived his messenger."~The Council of Elrond

Saruman is such an effective liar he completely deceives Radagast, which leads Gandalf to Isengard completely unaware that Saruman is a traitor. As Gandalf says himself, when first hearing Saruman wanted to have a little chat:

"And that message brought me hope. For Saruman the White is the greatest of my order."~ibid

And the thing is, it's not only two co-workers Saruman tricks, it's virtually everyone, as everyone was surprised by Saruman's betrayal...

The 'wisest' of the Elves:

There was a silence. At last Elrond spoke again. "This is grievous news concerning Saruman." he said; "for we trusted him and he is deep in all our counsels..."~ibid

Men of Gondor and Rohan:

In this way Saruman began to behave as a lord of Men; for at first he held Isengard as a lieutenant to the Steward and warden of the tower. But Frealaf was as glad as Beren to have this so, and to know that Isengard was in the hands of a strong friend. A friend he long seemed, and maybe in the beginning he was one in truth. Though afterwards there was little doubt in men's minds that Saruman went to Isengard in hope to find the Stone still there, and with the purpose of building up a power of his own. Certainly after the last White Council (2953) his designs towards Rohan, though he hid them, were evil.~Appendix A: The House of Eorl

From this we see Saruman is able to fool mostly all the "good" people up until Gandalf tells the Council of his imprisonment. It wasn't until afterwards when everyone realized Saruman had been deceiving them all and hiding his true intent. Afterall he had Rohan's trust, and Denethor had been counseling his father to listen to Saruman. But, can't put it any better than Gandalf's words to the Council of Elrond:

"Gandalf the grey caught like a fly in a spider's treacherous web! Yet even the most subtle spiders may leave a weak thread."

Saruman revealed his "true" mind to Gandalf, in hopes of persuading him, this backfired and Saruman's intentions became known. But, up until that point, boy what a 'treacherous web' Saruman did weave. Can you imagine how long he could have kept up his web of deceits had Gandalf not escaped?

Getting back to Letter 210 and Saruman 'corrupting the reasoning abilities', I wanted to point out this interesting part from The Voice of Saruman. First, let me add at this time Saruman's power was in a decline:

"But I fear your voice has lost its charm."~Theoden

I can go on and pull out all these various quotes where it shows Saruman holding the Men of Rohan under his 'sway' but the one section which I think truly highlights Tolkien's point in Letter 210 is here:

So great was the power that Saruman exerted in this last effort that none that stood within hearing were unmoved. But now the spell was wholly different. They heard the gentle remonstrance of a kindly king with an erring but much-loved minister. But they were shut out, listening at a door overhearing athe elusive discourse of their elders, and wondering how it would afferct their lot. Of loftier mould these two were made: reverend and wise. It was inevitable that they should make alliance. Gandalf would ascend into the tower, to discuss deep things beyond their comprehension in the high chambers of Orthanc. The door would be closed, and they would be left outside, dismissed to await allotted work or punishment. Even in the mind of Theoden the thought took shape, like a shadow of doubt: 'He will betray use; he will go - we shall be lost.'~The Voice of Saruman

Saruman's power is waning, yet his last effort was so effective he was able to weave a seed of doubt into everyone who could hear him. Theoden just got done telling Saruman to buzz off and he even had a thought that Gandalf would ally with Saruman!

I like morm's point about Grima, and considered him, since he is a Man. But, what made me ultimately chose Saruman was the fact that Grima was Saruman's pawn.