Okay, so first off, let me state the obvious here: I know we're on the internet and it's really easy to do, but don't look up quotes--that defeats the entire purpose. Be a good sport about it. 

Here's how this will work: one person drops a movie quote, bereft of context, and everyone tries to guess/remember which movie it's from. We keep it going from there. 

When offering up quotes, try not to make them too easy (No "Frankly, my dear, I don't give a damn" or "Do or do not, there is no try" type quotes), but also don't go for incredibly obscure quotes that no one's ever going to know because it's from a 1909 movie of which only two extant copies survive and you own one of them. 

If no one can guess your quote, feel free to drop hints. 

With all that said, let me get it started with one from a movie I saw very recently: 

"Tell them Captain Kazan knows that a horse has four legs, a murderer has two arms, but still the devil must fear one honest cossack."