The climax of the first scene of the final act, where Hamlet reveals himself to Laertes at Ophelia's funeral after having secretly returned home to Denmark. One of the greatest He's Back moments in all of literature.
Hamlet: What is he whose grief
Bears such an emphasis? Whose phrase of sorrow
Conjures the wandering stars, and makes them stand
Like wonder-wounded hearers? This is I,
Hamlet the Dane!