The final scene of The Tempest, where Prospero relinquishes his magic and frees Ariel.
Prospero: ...I'll break my staff,
Bury it certain fathoms in the earth,
And deeper than did ever plummet sound
I'll drown my book.
A production where a female Ariel spends the play in a visible harness, 'flying' on wires around the stage. When Prospero frees her, he unlocks her harness and instead of flying, she finally gets to RUN around the stage in sheer joy. So many tears.
A similar production with a female Ariel had her wearing all black, with a face-concealing hood and a mask over it — the latter of which she sometimes wore, and sometimes carried in one hand. At the end, Prospero took the mask and hood from her and threw them away, and she ran into the audience and straight out of the auditorium, laughing gleefully all the way.
It is made even more powerful by the fact that Shakespeare was himself speaking through Prospero. The Tempest was the Bard's last play.
His last good play; Henry VIII and The Two Noble Kinsmen followed — and it's believed by some reputable scholars that those were actually collaborations with other playwrights.
Nitpicks aside, The Tempest also contains the great speech beginning "Our revels now are ended...".
A production of the play in Stratford, Ontario staged Ariel's line "Mine would, sir, were I human" as a Wham Line. The look on Prospero's face was unforgettable.