Amazing movie, but the trailer doesn't do it justice. I've seen it about a billion jillion times.
The opening sequence is like a clinic on how to sum up entire characters using very brief vignettes. Johnny Boy's entire persona is immediately crystal clear in his first ten-second appearance, and there isn't even any dialogue.
"You don't make up for your sins in church. You do it in the streets. You do it at home. The rest is bullshit and you know it."