I usually go with:
Surprise: Holy Frijoles, Holy Guacamole
Frustration: Friggidy Frack, What the Frigg?
<sarcasm> But that is pretend swearing and is just as bad, I should be fired for doing it</sarcasm>
Our schools was renovated over the summer (yea they still are not finished). At the beginning of the year. I had computers (miracle there), kids (600 kids), IT working around me to set things up and boxes. I put the boxes under the tables and told the kids just to put their feet on them until I could sort things out. (We had maybe 20 hours work time from "end of construction" (still not finished) till the kids came in the building). My computers line the walls so I tend to walk in a big square behind the kids checking what they are doing.
I'm explaining something about the AUP, making an important point about safety and personal information. And I turn slamming into a chair the IT person had moved to get under a counter, go backwards and trip backwards over a box they had also moved, and land flat on my rear end. It hurt and I let out a hissss through clinched teeth counted to something like 50. While the IT people were fussing to see if I was OK.
That afternoon an irate parent came up to complain that I shouldn't have said anything, because it was pretend swearing and I just stubbed my toe. I pulled up my pants legs and showed the two lines of bruises on my legs. When she stomped off, my Principal and AP just burst out laughing. (Sometimes that is all you can do). Then they sent me to the nurse to be checked out - I was OK.
The ironic part - her oh so sensitive kid that my pretend swearing damaged for life - will curse a blue streak at us. Of course when he gets in trouble for it - we are racists violating his civil rights to use Ebonics as his cultural language.
Oh to construction before you started the TVs in each room were hooked to the stack in the library allowing us to show video's and DVDs to multiple classes. You ripped out the wiring even from the wing you didn't renovate - you are not finished.