One of my favorites from Amadeus:
"How does one kill a man? It's one thing to dream about it.. Very different when- when you... when you have to do it... with your own hands." - Antonio Salieri
I have a lot of favorite lines from books and film but that's one of the first that comes to mind.
Oh, here's more:
"To this day, people still come up to me and ask how I got over his (Sergei Grinkov's) death. My answer is always the same: 'I'm not over it.' In all honesty, I don't think I ever will be." - Scott Hamilton
"Nothing is either good or bad, 'tis thinking makes it so." - William Shakespeare, Hamlet
"Goodness is beauty in the best estate." - Christopher Marlowe
"There is no sin but ignorance." - Christopher Marlowe
"Money can't buy love, but it improves your bargaining position." - Christopher Marlowe
"O, thou art fairer than the evening air clad in the beauty of a thousand stars." - Christopher Marlowe
"Virtue is the fount whence honour springs." - Christopher Marlowe
"Who ever loved, that loved not at first sight?" - Christopher Marlowe
"Only the heart knows how to find what is precious" - Fyodor Dostoyevsky in The Brothers Karamazov
(I have been on a Marlowe kick the past few months LOL)