The idea here is to identify the movie quotes that are the most usable, not necessarily the best. For example, "Say hello to my little friend" is a great movie quote, but not necessarily usable that often. Conversely, the line "Alllllrightythen" isn't a great quote in the traditional sense, but it's infinitely usable. Just to kick it off, how about thise:
"I know funny, and that's funny" - Bruno Kirby in Good Morning Vietnam.
"As far as you know" - Chevy Chase in Fletch.
"WHOaah" - Pacino in Scent of a Woman.
I use these in everyday conversation all the time - well, you get the idea.