The best example of dramatic irony from the play is

when ophelia commits suic

when the audience knows that hamlet is faking madness as part of his revenge strategy, but the other characters do not; claudius, gertrude, polonius and ophelia have no idea why he is acting strangely.

when hamlet refers to claudius as a little more than kin and less than kind.

when gertrude drinks the poisned wine intended for hamlet.