I have a theory that each movie has a phrase or snippet of conversation in it which, to those who've seen the movie, can capture the spirit of the entire film. For exceptional movies, that line works even with those who have not watched it. Read the ones I've listed below, and if you can think of any others (assuming that you agree with my theory), let me know. Some movies may have more than one 'Line of the Movie', either of which can capture its spirit. Enjoy. (Fair warning: some are paraphrased as best I can remember.)
Source: Star Wars "Use the Force, Luke." OR "Help me, Obi-Wan Kenobi; you're my only hope."
Source: Empire Strikes Back "You don't know the power of the Dark Side!"
Source: Aliens "MARINES! We are leaving!"
Source: What Dreams May Come "I found you in Hell; what makes you think I can't find you in Jersey?"
Source: Starship Troopers "The only good bug is a dead bug!"
Source: Godzilla "We need bigger guns!"
Source: The Siege "We're the CIA; something ALWAYS goes wrong."
Source: Pretty Woman "It's not enough... I want the fairy tale."
Source: Fear and Loathing in Las Vegas
(which, by the way, is a BIZARRE look into the depths of the drugged-out human psyche!) "There he goes. One of God's own prototypes. Some kind of high powered mutant never even considered for mass production. Too weird to live, and too rare to die." -Raoul Duke
Source: Midnight in the Garden of Good and Evil
"It's like Gone with the Wind on mescaline. They walk imaginary pets here. On leashes. They're all heavily armed and drunk!"
Source: How High?
"Love dat shit, smoke dat shit, PASS dat shit!"
Another line that deserves mention is:
"How can I be failin' Women's Studies? I LOVE bitches!"
Source: Shatterdead (Note: This is the worst movie I've ever seen.)
Gun-totin' Susan: "Don't FUCK with me, dead bitch!"