Expressions that replace "Oh, my god!"

Heck, the place where somewhat naughty people go when they die.
Ruled with an iron spoon by Phil the Prince Of Insufficient Light.
“I darn thee to Heck!”

So, maybe “Phil darn thee” might be appropriate.

(Character has been blatantly stolen without permission from the Dilbert Universe. I am doomed now.)

Jumping Jehoshaphat!

Old Southern ladies will say “Oh shhh- sugar.” It’s the cutest thing.