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!"
What happens at St. Mere Eglise.
A minor one but Gen 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.