I can't properly answer this question, but if I did have a "significant other", I would probably call them by their actual name.. I really despise pet names for some reason, but I'm just weird like that. Maybe darling, that's acceptable, heh.
i just call him by name mostly - although he just never seems to get himself into a position to need to call me at all! we sometimes call each other bitch or whore. the only time i ever call him "baby" is when we're in bed.
this friend of mine calls her boyfriend "angel". i think thats sweet.