Who, in The Lord of the Rings, was the most effective liar?

[Raynor]

I wouldn't want my words to be taken just for granted , regarding the 160+ years:

Originally Posted by Tale of Years, RotK

2851, Third Age

The White Council meets. Gandalf urges an attack on Dol Guldur. Saruman overrules him. [It afterwards became clear that Saruman had then begun to desire to possess the One Ring himself, and he hoped that it might reveal itself, seeking its master, if Sauron were let be for a time.] Saruman begins to search near the Gladden Fields.
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July, 4, 3018

Gandalf imprisoned in Orthanc.

Originally Posted by Boromir88

Saruman still kept up his game of lying (lying quite 'effectively' I might add) even after everyone knew he was a traitor.

He also managed to successfully hide his intentions in his meeting with Gandalf, Galadriel, the hobbits et al, on August 28 - only to take over the Shire a month later. He still got the "skillz" .