1) What you say when you have nothing left to say to the person you are talking to, particularly towards the end of a fight. Usually meant to say that you couldn't care less about that person or what he/she does.
2) A way to call someone every nasty word you can think of without saying them all because the person you are saying it to either too stupid to understand any of them, or is not worth your time. In other words, it's like saying goodbye in a "fuckyou" fashion.
1) bitch: you're a cunt.
you: alright, that's fine.
bitch: oh, and I slept with your ex, just sayin.
you: take fucking care, bitch.
2) guy: I love you!
girl: I love you, too!
-1 week later-
guy: yeah... I met someone else
girl: well take care then!