For me the best line in this awesome film full of great lines is when Don Falcone says:
"You know right from wrong. You just don't care, and that's the most natural thing in the world."
That line in particular really sticks in my head and pops up quite a lot when I catch myself thinking cynically about the world. It's just about my favourite line in any film ever.
... I also like the line "Whatever happened to meat n' potatas?" It's a giggle.
Lena Olin's first line in the film: "Keep Lookin". Scared the hell out of me! It's all in the delivery. Also when she says, tears in her eyes, referring not to her first love, but her first hit, "You always remember the first time."
Oldman, referring to a waitress(?) who obviously hates his guts, "Ever since I sent her husband away...it's, like, she don't know me."
Big big fan of the movie for a long while- no one else I know seems to have seen it.
My favourite line is when Jack's buddy bumps into him in the toilet- and relays the story of Mona's escape with a rising, sweaty panic:
"She got my gun, man, she's running around with MY gun. Oh jesus Jack, they're gonna take my shield, they're gonna put me back in a f ucking uniform. You know what she did, Jack, you know what she did? She turned around and she pointed my own gun at me, Jack. SHE POINTED MY OWN GUN AT ME LIKE SOME KIND OF AN ANIMAL!"
Superb.
"Time is fleeting. What will it be? Toes. Take four." "You said Wednesday!" "Take two, we'll get the rest tomorrow."
All of those are great and the "Is it hard yet ba-by?" "It ain't easy." is just too ... cute! I think his manner of speaking AND accent were great in this film. The overly exaggerated NY accent can be a delight sometimes! That may help a line or two ...
I haven't seen this in 10 years, but still have it on my top 20. Agree with other poster that a surprisingly great number of people doesn't even know this dark and funny movie excists?
Being a philosophy student at the time "Romeo" ran in theaters I especially enjoyed Roy Schneiders "Moral distinctions can paralyse you" - always hang on to that when about to do somethimg wicked ;-)