I use fscker. Fizz-ucker! Also fark.
My mother is fond one of phrase in Ukrainian. When I finally asked her what it meant, she told me it’s ‘go to ass!’. I modified it to be ‘go to hell!’. It might come in handy for a bad slashfic though! 
Let’s see…I will say things like blast, rats, drat, sticks (from an elf-centered romance novel–the elves said this all the time, causing much amusement to the various human characters), farg, farging farg, bacon lettuce, and dang. I’m not much on swearing in general. I basically only swear in dirty talking situations or when I’m really, really angry.
“Hell’s own dreadful bells,” or “Hell’s bells.”
“Gods below!”
“What in the…?”
“Oh my.”
“Crap.”
“OH MY GOD!” (Funnily enough, this is the one that I instinctively went for when my two fuzzy not-so-little bastards knocked my COMPUTER over. Especially since it was still running at the time. :eek: )
Well - son of a biscuit eater!
I swear in Spanish, or rant in Spanish. Some cuss words, some nonsense. It serves me well where I work (which is the only place I try not to swear) because the people I work closely with speak English exclusively. Beyond that, all fuckin’ bets are off! 
I like it too. Even “Bunny Nuts!” could work well.
At work I tend to say, “Oh poop!” a lot. I picked it up from my stepsister. I think it was always so funny to hear her say it because I knew what foul language she was really capable of.
“Consarn it!” may also bring relief. 
Some of my favorites have been mentioned; piffle, son of a biscuit eater, God bless America. Other favorites; Jumpin’ Jeebus, Great Guano.
Also, from my when my niece was very young, oopie doopie. Years later, I was still using that one. My co-workers had heard me use it and several variations, but rarely an actual cuss word. Then, one day I was overwrought and burst forth with “Fuck me!” When my office-mate expressed shock, I said, “What did you think oopie doopie meant?”.
Just remembered a couple more of my favorites:
Shucky-darn!
Sugar-booger!
Yeah, not too impressive…
I do swear a lot - so I have to use all the usual sugar and feck type disguises. I cheat and swear in other languages when it has to come out - sorry about the phonetic spelling here folks … I use
the Dutch “hod fer dommer”
Greek “haaaaamoteee pana jesu” - usually only need the first part
Irish “pogue ma hone”
And I adore the french “ooooo pah” when you lose your balance and plummed head long into the wall
Fargin’ Sons Of Bastitches!