Favourite quote? Ooh. Gosh. Dunno. I mean, I can quote stuff, and do, extensively, but an absolute favourite? Well, both "sorry about your barn," (from Back to the Future and "and that makes you my new best friend," (from Titanic - I can say that now that someone's got it right) are both quotes I like to get into casual conversation - the former with a more relevant noun replacing "barn". Similarly, "this must be Thursday; I never could get the hang of Thursdays," with [insert relevant day of the week here]. And from the same source, "Life? Don't talk to me about life."
I could be all pious and go for a Biblical quote, but actually, while there are a few I like, there are none I could guarantee getting absolutely right. Well, apart from John 3:16. Maybe. And that would depend on which version you were using.
I think I'll go with four (I know. Greedy) from Doctor Who. Quelle surprise.
"Let me get this straight. A thing that looks like a police box, standing in a junkyard – it can move anywhere in time and space?" (Ian Chesterton to the Doctor in the very first episode. I think that perfectly captures the wonder of the show, 50 years on.)
"It's the end...but the moment has been prepared for." (The fourth Doctor's last words before his regeneration. I imagine many people who were of about my age at the time - I was 11 - will testify that it was a very moving scene.)
"I can't stand burnt toast. I loathe bus stations - terrible places, full of lost luggage and lost souls. And then there's unrequited love, and tyranny, and cruelty." (The seventh Doctor, asked by Ace what he hates. It's a small line, but I find it has a poetic beauty to it.)
"There are worlds out there where the sky is burning, and the sea's asleep, and the rivers dream. People made of smoke, and cities made of song. Somewhere there's danger, somewhere there’s injustice, and somewhere else the tea's getting cold. Come on, Ace — we’ve got work to do!" (The Seventh Doctor to Ace at the end of Survival. A poignant farewell to the classic show, and it was my favourite bit of More than 30 Years in the TARDIS.)