Well, hmm, now how did I miss out on such a classic post? (Oh yeah, heh, I don't log in that often...
.)
For BG1 vanilla, apart from Umberlee-related references:
#3493 [KIVAN 31] You dark-hearted bitch, you'll die for that.
#4301 You're those bastards who've been taking down our mining ops. Well you've come to the wrong place kiddos. I'm one mean son of a bitch, and I'm gonna give you a world o' hurt.
#6442 Life has been pretty lousy lately; how about you friend? My bitch of a wife slept with some elvish mongrel, and even had his child. By the Nine Hells, does she ever have gall. Anyway, she's not laughing anymore; I cursed the child of that unholy union, so that it would die an early death. I hope the little brat drowns in its own vomit.
#8921 [Letter from Sarevok to Slythe] ... Make sure to keep a leash on your little bitch of a wife...
(Used a lot in its traditional sense to refer to werewolf women in TotSC as well)
As for BG2 and EE(2), probably a lot more... didn't check. But I think you can assume that any sort of commonplace curse can get rendered into "Common" as it would've in pre-modern i.e. medieval times (and such words were just as common back then, as some of the oldest "curse" words were).