In Act Five, Scene One of A Midsummer Night's Dream, Theseus asserts, "No die, but an ace for him," while watching the Pyramus and Thisbe play. This is a pun (although not necessarily one that translates well into modern English!) because "ace" used to be pronounced like "ass"; thus, Theseus is unknowingly playing off the fact that Nick Bottom--who is now playing Pyramus--had been turned into a donkey earlier in the text.
In Act Two, Scene Two, Lysander responds to Hermia's request to "Lie further off yet, do not lie so near," by riffing off of "lie": "For lying so, Hermia, I do not lie." This is a pun in that Hermia meant one definition of "lie" (to physically lay down somewhere), whereas Lysander is using the word to testify to his own faithfulness.