Oh Crap/Theater

• In what might be a "Crowning Moment of Oh Crap", Macbeth has two of these when it dawns on him he might've taken the witch's truths a bit too literally...
  • Or, more accurately, not literally enough.
• The last scene of Hamlet has a couple of these. Hamlet has one when Laertes informs him that he's been poisoned by the foil and he's got less than a half hour to live (a lot less, as it turns out). Claudius gets the next one when it becomes clear that the jig is up, Hamlet is finally sufficiently motivated to kill him, and no one's about to prevent it.
• Angels in America: Roy's death scene
• Enjolras in Les Misérables gets one when he realizes that Les Amis are about to get obliterated by the French Army because no one has come to their aid.

The people have not stirred
We are abandoned by those who still live in fear
Let us not waste lives
Let all women and fathers of children go from here

• In John Willard's "The Cat and The Canary", lawyer Roger Crosby has one of these moments as his last line"
  • As does Charlie, when he is unmasked by Annabelle.
• How is Spring Awakening not here already? They have an entire song about this trope.
• Sir Ruthven Murgatroyd from Ruddigore has three: When Richard unmasks him (forcing the title and its Be A Punch Clock Villain Or Die Horribly curse onto him), one when he realizes his misdemeanors won't cut it and he has to cross the Moral Event Horizon or die, and again when Dame Hannah, the maiden Gideon Crawle has kidnapped on his orders, appropriates a BFS and challenges Ruthven.
• In The Taming of the Shrew, Lucentio has switched places with his servant Tranio for the purposes of a Zany Scheme. Eventually, Tranio is told to produce his father and gets a pedant to impersonate Lucentio's dad. Everything's going well until Lucentio's real father shows up, at which point Tranio, the pedant, and Lucentio's other servant Biondello frantically deny knowing him and try to get him thrown in jail. Just when it looks as if this might actually work, Lucentio arrives on the scene:

Biondello: O! we are spoiled and--yonder he is: deny him, forswear him, or else we are all undone.
Lucentio: [Kneeling] Pardon, sweet father.
Vincentio: Lives my sweet son?
[Exeunt BIONDELLO, TRANIO, and Pedant, as fast as may be]