I fall back on Mork from Ork’s classic:
“Shazbot!”
“Nimnul!”
Acquired from a young priest in Catholic high school, “God Bless it!”, I figured it would help balance out the other diametric opposite I often used.
“Oh, biscuits” [general curse word] and “Cheese and Crackers!” [I assume this is a direct replacement for ‘Jesus Christ!’] are favorites of mine–if I use them consistently I’m less likely to swear around my kids, 6 and 9 years old. These are the family-friendly phrases of choice for the Australian kids show “Bluey.”
“Furshluginer” is a good’un.
So’s The Muttley Mumble from the Dick Dastardly cartoons (Muttley was his dog, kids): “Shaggafrashnbaggnmacknsackawakkagrrrrowf”
Clockslacker
Farging Icehole (from some movie, I think)
Bastridge
Mother-Scratcher (from another move)
Johnny Dangerously. Also “farging bastadge.”
(Do you know your last name is an adverb?)
I have a friend who says vacuum instead of f___ you.
I always transliterated that as Rockemsockemfrickemfrackemrazzlefrazzis.*.
Hey! I got my cake day post in!
Dagnabbit, I can’t really shive a git about it.
What the fudge?
Whisky Tango Foxtrot!
Grumble (yes, I say the word)
I’m fond of “Oh, my stars and garters!” myself.
And “motherjammers”, which I picked up from a Key & Peele sketch.
I used to toss razzenfrats about liberally. And spousal unit and I will call certain folks cheese logs because it works.
Stoopit cheese logs…
Only a mild swear, but when the kids are misbehaving I’ll ask them to stop acting like a bunch of jackelopes instead of jackasses. While jackasses isn’t that bad, it’s less obtrusive in public.
“Frickin-A!”
“Fook you” and “fook me” (from Austin Powers).
“Holy schnikies!” (from Tommy Boy).
“FTS” for fck this sht! or fck that sht!
That’s mine and I really emphasize the F
Shuckin’s.
Judas Priest on a pogo stick!
cork soaking
bunghole
mother trucker
. . . and the horse you rode in on
from Battlestar Galactica: “frack” and “felgercarb”
I am rather fond of “frig” and “bugger”. Most Americans don’t know what the words mean, so they think you are using a euphemism. Actually, both words refer to specific sex acts.
Anything available in languages other than English is also welcome.
French has many euphemisms. I think Spanish has fewer, even though Mexicans have been known to swear from time to time. 
I believe, although I’ve no data for this, that Australians swear (or “curse”) more readily than most Americans. Regardless, I’ve taken to calling bad drivers “poltroons”. (As in “oh, you poltroon!”).
“Fuccryin’ out loud” is another good one, as is the old hippie phrase “Far out” – preferably in a Californian accent, and with “man” tacked on the end. (Far out, myann!) A couple of “Sht" substitutes: “shoot” and “Schweppes”. Instead of using "Motherfcker”, we’ve taken to using “incestuous” (“you incestuous thing”!). “Holy potatoes, Batman” is another good one for when I can remember it.
And a couple of Inspector Hastings-isms, from the British Line Of Duty series (apologies to Christians): “Holy mother of God” and “Jesus, Joseph, Mary, and the little donkey”.
Not a swear (or curse) word, but “Rack off, Noddy” has a peculiar Australian history that I won’t bore everyone with.
snap!