This is based on opinion. Please don't list it on a work's trope example list.
Tear Jerker / The Longest Day
"Where's Johnny? He's borrowed my boots!" "At the bottom of the Channel."
"I wonder what 'bitte, bitte!' means?" It means "please, please!"
"Two clicks... I heard two clicks!"
Some paratroopers were dropped too far from their target zone, falling on the town of Sainte-Mère-Église instead. Said town is heavily garrisoned by German soldiers, and the paratroopers get mercilessly mowed down — some even before they have a chance to land. And all Private John Steele (who got his parachute stuck on the church bell's roof) can do is watching his comrades die. He's clearly seen crying, and gets deafened by the church's bells, on top of this.
A minor one but General Roosevelt leaving his superior's office (After reassuring said superior that his health issues would not be a problem) and picking up a cane. Even moreso when you know he died a month later.
The final dialogue.
It's funny isn't it? He's dead, I'm crippled, you're lost. I suppose it's always like that, I mean war. I wonder who won.