I started using a nickname, because I wanted to annoy him and he started giving me one as well.
Most Helpful Guy
One kept up some pretty insulting nicknames. She didn't mean it as insulting as it appeared, but I told her not to, (it happened to be a nickname I also had in grade school, so there was a lot of history with the name and a bad childhood) and she just kept it up. I dropped her fast.
Babe (unless she calls me that because I remind her of the pig), hon, sweetie, all fine. I hate "Bae" or ultra cutesy nicknames (I only use them ironically) ("Schmoopie.")
It kinda depends on what it is.
Most Helpful Girl
My current nickname is "moo moo"
Literally being called a cow. (Context being that my boobs have sprouted as if from nowhere in like 2 weeks, 'cause pregnancy hormones)
It's obviously not mean-spirited in any way, but I have mixed feelings about it.