How do they swear?

I've been spending some time getting caught up on Writing Excuses, and one episode on polytheism brought up an interesting question. A couple of the panelists said that when they are first thinking of a new religion, they start by wondering what their characters would swear by. That got me thinking in a different direction about character development - how do they swear?

Last year I read a book about the history of swearing in English, and the book broke things into two categories - the profane and the obscene (or rather, the holy and the shit of the book's title), and charted how these two categories rose and fell in terms of how "bad" they're considered by society.

Its says a lot about a person's beliefs with how they treat these two categories - I have family members that will take God's name in vain, but would rather be mute than reference any bodily function or fluid. On the other side, I've worked with people who had no problem dropping f-bombs on a regular basis but would twitch any time they heard someone say "Oh my God."

Swearing is one of those aspects of language that people tend to have definitive ideas about. Growing up, I was under the impression that the only people who swore were "bad" people, and even saying something that could be misconstrued as a swear word was to be avoided. (I may or may not have gotten into trouble for calling for my cat by saying "Puss puss!" Mom meant business.) I had to come up with some kind of "filler" words, because you still need something to holler when dropping something on your foot. I tended to go either cutesy (fudge), old-fashioned (blast), or British so no one will yell at me in the States (bollocks).

So when thinking about a character's voice, imagine they've dropped something on their foot. How do they react? Why?