I really scenes where people choose to take heroic last stands, especially if they represent a morality upgrade. I'll give 100 for the first 10 good suggestions (even if I've seen it, as long as it's not one of the examples). 50 per after that until I close it.

I've included movie clips because they're easiest, TV and books are also acceptable.

Guardians of the Galaxy: I have a plan https://www.youtube.com/watch?v=O5qPifYpeOE

Guardians of the Galaxy-"I have a Plan" Scene

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Serenity: I am to misbehave https://www.youtube.com/watch?v=1VR3Av9qfZc

Gettysburg: Bayonet charge https://www.youtube.com/watch?v=ZL-5uyp44WA

Note I've already checked TVTropes and no trope quite cuts this quite at the joints.