My husband used to say Daggommit all the time until when our daughter was two she tried to repeat it and it came out sounding like....G..D..... needless to say he had to nip it in the bud. haha
I have a list but I usually come up with "good grief Charlie Brown" (which my daughter the Sailor can't believe I say), or blast it, or horse feathers or Bull Funky which I got from Whoppie.