The first five quotes I could think of.
"And as long as I have one ass instead of two, I'll wear what I like, if that's alright with you" (Erin Brockovich, Erin Brockovich)
"If the right honourable gentleman could perhaps attend more closely to what I'm saying, rather than how I'm saying it, he may receive a valuable education in spite of himself!" (Margaret Thatcher, The Iron Lady)
"Whoever said orange was the new pink is seriously disturbed" (Elle Woods, Legally Blonde)
"Oh come on. It was just a little bomb" (Jane Smith, Mr & Mrs Smith)
"Always" (Severus Snape, Harry Potter and the Deathly Hallows, Part II)
Other favourite quotes I can think of:
"Oh don't be silly, Andrea. Everybody wants this. Everybody wants to be us" (Miranda Priestley, The Devil Wears Prada)
"I can fight you!" "You will lose." (Father Flynn / Sister Aloysius, Doubt)
"I don't know, I've been told I'm a pretty good writer. Already sold a lot of books!" (Aibileen, The Help)
"You a Godless woman" (Aibileen, The Help)
"I've always wanted to use that spell!" (Minerva McGonagall, Harry Potter and the Deathly Hallows, Part II)
Among so many others. These are all my favourite quotes because they show just how amazing and awesome the characters really are; they define both the characters and the movies and they give me chills each time. The last one is arguably a more comedic moment, but it qualifies regardless. That is the magic of Harry Potter films :P
If you have any idea how long it took me to come up with this list, you'll know that I really suck at quoting things - mostly because I believe that nobody should. I remember quotes that move me all the time, but as a general rule I think quoting anything should be kept out of conversations because it is so lame. So many of what should be classic movies (and even modern ones - read: The Hangover) have just been totally destroyed in my eyes because people didn't know when to shut the hell up and stop quoting them. "Here's looking at you, kid" and "Frankly my dear, I don't give a damn!" are perfect examples.