There are two major examples of Tom outright lying or deceiving people in "The Great Gatsby". The first is in the beginning of the novel when Tom is having an affair with Myrtle. While Daisy may suspect or have been told about it by others, Tom has not come out and been truthful with Daisy about his affair or perhaps the reason behind the affair.
Tom also lies out right to George Wilson, saying it was Jay Gatsby who was driving the car that killed Myrtle, and not Daisy. Though his protection for Daisy, and perhaps Daisy herself, prompted Tom to lie in this way, the lie resulted in Gatsby's death (which may or may not have been Tom's intention in the first place).
There is an example of Tom's deception in Chapter Two when he and Nick are having a party in the New York. According to Catherine, Tom will not file for divorce (and be with Myrtle completely) because Daisy is a Catholic and does not believe in such practices. Nick is shocked by the "elaborateness" of this lie: Daisy is not a Catholic and it is far more likely that Tom simply wants to have both women. In this case, his deception is an expression of his arrogance. Similarly, Myrtle Wilson deceives her husband by having a secret affair with Tom Buchanan. For her, the affair is about improving her status and escaping the confines of the Valley of Ashes.
In contrast, George Wilson does not use deception in the same manner as Tom and Myrtle. As we see in Chapter Eight, George acts as a reminder that lying is not always the right thing to do. This is shown when he reveals to Myrtle that he knows about her affair:
“I spoke to her,” he muttered, after a long silence. “I told her she might fool me but she couldn’t fool God. I took her to the window.”