Our group is filled with players who watch A LOT of movies. Tons and tons of movies. So we quote it all. Sometimes, a player will use a really obscure quote just to put forth an on the spot challenge to see who can name where it came from first.
But, I'll tell you some sources that seemed to come up the most.
>>Star Wars: but not during a Star Wars game and not the main quotes. Usually stuff like, "He's got too much of his....FATHER....in him" in a exaggerated Aunt Beru voice and with a slight perveted suggestive nature when saying the word "father". Usually said in regard to the main villian. Yes, we're disgusting a lot times.
Or if we get into a horse drawn wagon filled with goods we're trying to get away with, someone will jump on the driver's bench and say, "Punch it Chewie!"
>>Lord of the Rings: c'mon, this is D&D isn't it? Its bound to show up in our games. But again, in the wrong places. Like if we're at a bar and the fighter needs to resist the temptation to drink. He's got be able to fight later! So of course the barmaid will keep pestering him if he wants to order a tankard. This is where we use things like (in the best Gandalf voice we can do and real over the top), "Do not tempt me!"
Maybe even keep going with the same lines from the same scene. Look seriously at the barmaid and say, "Through me it would wield a terrible evil!" Then the barmaid would be like, "Ooookay, just asking if you wanted a drink."
>>HEAT, yes the LA crime story with Deniro and Pacino. This gets quoted the most I think. Weird huh?
"She's got a GREAT @$$! And you got your head...ALL THE WAY UP IT! Fierce aren't I?"
"C'mon brother, its a substance abuse problem...."
"You can get killed walking your doggie!"
"GIMME ALL YOU GOT!!"
While snapping fingers, "Keeps me on the edge, where I gotta be."