http://www.urbandictionary.com/define.php?ter...
Holy Toledo
12 up, 4 down

Most likely first used in the early 1900s, either refers to a sarcastic remark about Toledo, Ohio or originated from a realistic remark of the Holy city of Toledo, Spain. It is now used as a phrase, by Americans, if something is unbelievable, disturbing, or blows their mind

And many more to come.

Da gibt's vieles, das, je nachdem, wie man's ausspricht, leichten Sarkasmus oder echtes Erstaunen andeuten kann. Hier nur ein paar Beispiele:

Would you look at that!
Ain't that something!
You don't say!
Well, I'll be!
I'll be a monkey's uncle!
Holy cow!
Un-fuckin'-believable!
Ain't this a kick in the head!

"I'll be a monkey's uncle!" (old-fashioned)

Something that you say when you are very surprised:

"Well, I'll be a monkey's uncle. I never thought Bill would remarry."

from: http://idioms.thefreedictionary.com/I'll+be+a...

Really old-fashioned?

http://www.worldwidewords.org/qa/qa-hol1.htm
[Q] From Lee Daniel Quinn in the USA: “I thought the question was an easy one — where does the term holy smoke come from? It may be an Americanism because I have heard it all my life. Any ideas?” [...]
It seems more likely that holy smoke was invented anew as a mock-religious exclamation and mild oath on the model of the older holy Moses (from the 1850s), and holy terror and Holy Joe (both from the 1880s). In turn these probably served as the model for others of similar type that came later, such as holy cow from the early 1940s.

"Holy smoke!"