It's the bye you say when you don't wanna f*ck with a certain person anymore.
P1: You're a police officer now?
P2: Yeah, been on the force for 8 years now.
P1: Never would have thought you the type, what with that incident back in the day...
P2: Riiiiight....take care.
Person notes this when leaving room and says "take care" to this person, perhaps instead of have a good one or have a great one which would be more up beat.
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.
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!