Mercutio: "Ask for me tomorrow, and you shall find me a grave man." His dying line is a pun! I should hope to die so well.
Friar Laurence's Get a Hold of Yourself, Man! speech to a hysterically suicidal Romeo in Act III Scene II; he reminds Romeo that he was lucky to be banished instead of punished by death, lucky to have killed Tybalt when Tybalt tried to kill him, and killing himself will essentially kill Juliet.