Most of us do it, and there are many forums debating the issue of atheists 'taking the lords name in vain', so no need to rehash it here, unless you seriously feel the need...
I still fall back on 'Jeezus Christ' and goddamn thisorthat when I'm really flustered, but I've become more creative when I'm feeling squirrelly...
Darwin Dammit...By the bones of Galileo...or heebie Jebus momma...I still like Fuckit the best
I tend to use more and more "English" slang (as opposed to "American") as Sam here points out, remarkably useful and very colorful, you can also use a lot of it in "polite" company here in the US and no one is the wiser.
When I must retort to such idioms like "in the name of god" I always add a twist like "whatever god" or "if a god exists". Sweden is a good language in terms of swearing. We don't say Jeeeezus, we say Satan :))
One of the best is "faaaaaan satans jävla helveeeeeete!" which is something like "fuck Satan's fucking hell". If 100% correctly translated, "fan" is the word for a lesser evil or devil, probably originally related to the word faun in Greek mythology, "satans" is "Satan and the "s" at the end means it's in genitive form. Swedish also add s'es at the end of words to mark genitive just like English. "Jävla" is a fun word, because there is no equivalent in English. The best translation is "fuck", but the word is a derivation from the word "jävel" which in turn is another form of "djävul" which is correctly translated as the devil. A person who is a "jävel" is a person who is so good at something he/she could as well gotten the skill from the devil, basically. "Helvete" is the Swedish form of Hell, so "jävla helvete" has a very specific meaning since it is a place like no other. Quite unique but in a sort of positive way. While "jävel" has an original negative connotation since it is derived from a negative word, it has almost taken upon the properly of "godly" or "godlike", while still pointing back to the devil and devilish powers.
Interesting eh? Anyway, it's is by far the best swearing in Swedish. The more common though are words like "fitta" and "kuk", basically "cunt" and "dick". For some reason though, "fitthelvete" has gotten quite a big place both by males and females which basically means "cunt hell". Swearings are so funny when you start to look what it actually all means! I mean, why do Swedes focus on the female organs when English people focus on the male ones? I mean, take things such as dickhead. I would be surprised when I see cunthead!
Anyway, if it's English, fuck is rather commonly used by me. I never seriously swear when I use idioms such as oh my god, more when surprised or shocked.
Well, fuck is probably the one I use when I am seriously pissed and angry. Fuck off has a nice and aggressive connotation.