There are two sayings commonly used when one departs from another person or passes another person in New York City that seem to be specific only to the region.
One is "Get home safe." Also said "Be safe getting home."
People routinely say this when you are going home at night. I have never heard it commonly said anywhere else. It kind of seems foreboding, like they are reminding you of all the terrible things that might happen. Probably it became commonly said back when New York City was a more dangerous, less gentrified place. Frequently strangers will say this to me when I am leaving work, school, the subway train etc. Also people will say it to me when I pass them walking down a city street at night. In this context it seems to be mean "What are you doing out so late! It's dangerous! Go home now!"
Another is "You have a nice day now." (and other similar rephrasings.)
But the weird thing is that it is usually said by strangers who have not spoken to me at all. Who will just say it when they exit whatever public space we are inhabiting, especially when they are exiting the train. It always seems a bit weird to me. Last time it happened, I was reading a book and some guy on the train I hadn't even noticed said it to me as he was getting off. It makes no sense to me as it seems to be something you would only say to someone you were speaking to. When I am walking down the street people will also say it to me as I pass them--most of the time men. It seems strange to say such a thing to a total stranger. Maybe it's some polite variation of "hey girl! How you doin'?" Except it's sort of final, like the end of a conversation, not the beginning, so it really does not function as a segue way or pick up line.