In Ayn Rand's play Night of January 16th, Karen Andre, accused of murdering Bjorn Faulkner, is nearing the end of her testimony, when the Surprise Witness barges into the courtroom. Karen frantically tries to prevent him from saying anything, but he tells her, "Your sacrifice is useless: Bjorn Faulkner is dead." Karen faints from this revelation, and the curtain falls on the second act.
There's another one in "Hasa Diga Eebowai". The first 15 or 20 minutes seem like a complete comedy that just glosses over any darker issues, but then, in the middle of all the hilarious blasphemy, the Ugandan villagers sing directly to the audience, "If you don't like what we say, try living here a couple days. Watch all your friends and family die—hasa diga Eebowai!" It's the first indication of the show's quite serious themes.
The end of act I of David Mamet's Boston Marriage: "She asks why you are wearing her mother's necklace".
Humble Boy: "Mother?...Mother, please tell me you can see him."
Cabaret: "But if you could see her through my eyes...She wouldn't look Jewish at all."
Hamlet: "...revenge his foul and most unnatural murder."
Godspell: "This is the beginning."...of the end. Jesus says this to tell the community that was built during Act 1 that he's going to leave them to see if they retained the lessons learned from his teachings. And it all goes downhill from there, ending in His Crucifixion.
Also, the line right before "On the Willows": "And I tell you I shall never again drink from the fruit of the vine until I drink it again with you in the Kingdom of my Father." Jesus then says goodbye to the rest of the cast.
"Then the man they called Judas Iscariot went to the chief priests, and said "What will you give me to betray Him to you?" They paid him thirty pieces of silver — and from that moment, he began to look out for an opportunity to betray Him." (Matthew 26:14-16, KJV) The line signifies the transition from John to Judas.
The final line of the speech is accented with a percussive sound not unlike Dramatic Thunder.
From Wicked: 'You have no real power,' as well as a WHAM moment when Glinda shows the Wizard Elphaba's keepsake, identifying him as her father, moments after having had her murdered.
Another one takes place at the end, at the site where Elphaba made her last stand. The Scarecrow comes on stage, knocks on the floor, and says two words: "It worked!" Elphaba, alive and well, comes up through a trap door and reunites with her beloved Fiyero before they make plans to flee to Earth.
From David Auburn's Proof: "I didn't find it. I wrote it." End Act 1.
Next To Normal: "Whose birthday is it?" "My brother's." "I didn't know you had a brother." "I don't. He died before I was born."
RENT: "AZT Break." How Mimi reveals to Roger she has AIDS.
Sunset Boulevard actually has a Wham Song, specifically "New Ways To Dream (Reprise)," in which Max fills in all the remaining holes relating to Norma's past. The biggest Wham Line within the song is probably "Please, understand, she was my wife."
tick, tick... BOOM!: Jon gets angry with his best friend Michael and screams, "What the hell do you know about fear? What do you know about anything?" Michael responds, "I know I'm sick, Jon, and I'm not going to get any better."
Sweeney (Theatre Version): Oh, God! "Don't I know you", she said... You knew she lived...! From the first moment that I walking into your shop you knew my Lucy lived! Sweeney (Film Version): "Don't I know you", she said... You knew she lived... You lied to me.