I freely admit, I don't curtail my use of profane language. I try to be respectful of the company I keep - like my mom, for example - and shut my mouth when it is in the vicinity of 'little ears'. And I've never been one to shout "Jesus Christ!" as a cuss word. It's just not one of my words.
But the New Testament is rife with discussion as to what kind of speech is appropriate for Christians. (This IS a religion discussion thread, after all). The passages which admonish Christians not to engage in coarse joking, profane language, filthy language etc (depending on your translation) suggest to me that the "line" is drawn where your best judgment lies. Obviously what is vulgar in the first century will be different now, and I suspect that THAT is why it isn't SPELLED OUT. (I'm reminded of the Shakespearean play where biting the thumb is considered an insult; obviously, it isn't, now).
It's never supposed to be "these are the things you can utter, and these words you may not". It's always been "this is the kind of person you should be, and this is not". You're grown-ups, in the New Testament. Use your own sound judgment.
You know, it warns people to be slow to speak, and to be careful what kinds of ruin you can bring to yourself and others if you don't watch what you say (context is NOT discussing cussing, however). It tells Christians to bless those who revile them; they are to be gracious to those who mistreat them in order to prick their consciences; or as it says "so as to heap hot coals on their head" as a metaphor.
So, when you wonder, does the Bible say I can't say Sh$t, the real thing a Christian should ask is what SHOULD I say, and use the good sense God gave him. It may sound trite, but the What Would Jesus Do principle is the best yardstick.