"Broke into the wrong goddam rec room, didn't you!"
From "Tremors". Usually use it when I get a mosquito before she gets me.
"Never mind the phones, Heinrich."
From "Das Boot". Usually use it when some project goes south and you know you're about to get depth charged. Says a lot about not needing to be too technological when you can already hear the destroyer's screws overhead.
"You'd think that sometime, the dam surf would just lay off for a little while".
From "Mr. Hobbs Take a Vacation". Jimmy Stewart says it when trying to get to sleep after a tumultuous day late in a beach vacation, after he had raved about the pleasant sound of the surf earlier in the vacation.
Also from Mr. Hobbs, stated by his son-in law's boss who has taken Mr. Hobbs out bird watching for the first time, when Hobbs keeps thinking he's spotted some exotic new species. We use this one often while bird watching.
"He was your what, Miss Paquette? He was your WHAT, Miss Paquette?!"
From "Anatomy of a Murder". Used when talking about verbal land mines people are about to trigger.
"Goddammit, Grady, I am the President!"
From "Fail Safe". USed when you're trying to clinch an arguement with someone who fails to see the power of your own logic.
"Don't blow it, Louise."
From Thelma & Louise
And one of my personal favorites:
"It's not smart to play blackjack if you don't count cards."
From: "Hard 8"
Also, in response to Celtaddict:
"My, that IS a big one," is from Dirty Harry, re Harry's S&W .44 mag.