I have two.
Does anyone I know own a marmot? No. Have I ever seen a marmot? Maybe in a zoo. I don’t know, but I’m dying to use this line. I may have to go to a zoo just to say “nice marmot”.
This never seems to come up, for some reason. Foo. It’s such a good line, too.
“Bring him to me! I want him alive!”
God I must say that at least three times a day. Funny enough “I will spare your life” doesn’t come up a lot…
“Illinois nazis? I hate Illinois nazis.”
From White Mischief (directed by Michael Radford), when nothing is going right, spoken slowly and of course ironically:
“Another fucking beautiful day.”
(Sorry not strictly within the OP guidelines, since I get to use it a lot.)
I only need something to happen involving a pair of things to say:
“Shoot 'zem. Shoot 'zem both”
Sit tight, hold down the fort, and keep the home fires burning. If we’re not back by dawn, call the President.
Jack Burton has lots of great lines, but that’s the one I find most useful.
‘Jack, you have debauched my sloth!’ - HMS Surprise
I don’t suppose this one comes up too frequently.
“I am gravely disappointed. Again you have made me unleash my dogs of war.”
I have no idea why, but I use that every time I have an opportunity (complete with the accent). Oddly enough, I had one just the other day. Yes, people look at me funny, but I’m used to that. 
muldoonthief, he sure does, don’t he? That is one of my favorite movies of all time!!
“Yippee kai yay muther fucker” Whispered under my breath while squezing the trigger on a target 1000 yards away.
“I’m okay”
In an SNL where Maya Rudolph plays Donatella Versace hosting a Halloween party, she says, “What is that squeakin’?” in this perfectly drunk voice.
You would not believe how often this line comes in handy.
“To crush your enemies, see them driven before you, and to hear the lamentation of the women.”
Doesn’t come up much.
“Smoke me a kipper, I’ll be back for breakfast!” Arnold J Rimmer - Space Adventurer.
I have used this… probably too often.
Wouldn’t it be more appropriate to say it in the presence of a ferret?
“Its made from monkey cum you know” from the kids in the hall movie, Brain Candy i think… i wish i could use that more often. Oh and “im so glad i shaved my balls today” from Hostel when something unexpectedly good happens.
“Don’t make me get my flying monkeys!”
I get to use this every once in a while with my kids.
“Maybe we should just give him another one of out ancient Goblin made swords?”
From the Latest Harry Potter book.
“I swear to God I’m going to pistol whip the next guy who says, ‘Shenanigans.’”
“Oy with the poodles already!” I can’t help it, I love Gilmore Girls.
Bathe her, and bring her to me.
I like you. I’ll kill you last.