In Hamlet, many of the characters are deceptive, with their behavior hiding their true selves or motives. Which characters in Hamlet do so?I know...

Concerning Shakespeare's Hamlet, I'll add the one character that isn't mentioned in the previous answer:  Hamlet himself.

Though he resents his mother asking him why he seems to still be so troubled by his father's death--he goes on a bit of a rant because, he says, he just doesn't seem to be depressed, he is depressed (Act 1.2)--he actually does plenty of acting and pretending in the play himself.

Most notably, he announces that he will put an antic disposition on (pretend to be mad or insane), and then he does it.  His mistreatment of Polonius, Ophelia, Ros. and Guil., are all done under the guise of madness.   

Plus, he arranges for the players to perform a murder scene that mimics what the Ghost has told him about his father's murder, then watches intently the king's reaction, in order to determine the king's guilt or innocence. 

He also, presumably, acts like nothing has changed, to Ros. and Guil. once he turns the king's plot to have him executed against Ros. and Guil.

Hamlet, who seems to detest the deception others would employ against him, certainly practices his share.