"Oh, for God's sake" is a curse and could be considered rude, especially to religious people as the word God in this use and any other English use is referring to the religious use of God. "Aw, for Pete's sake" is like a polite version of the above (more polite anyway and still far from professional). Aw and Oh have no real meaning on their own except to express anger or frustration in this case, so you could say "Oh, for Pete's sake". There are other variations of this like "For Heavens sake", "For Jesus sake" and "For Christ sake"... but again we are talking about Heaven and godly figures in a religious sense and so religious people (and others) could get upset. Why Pete you ask? That's a good question and I guess it's best to think of this as an Idiom. I'm not sure where it comes from but If I had to guess I would say that it comes from "St. Peter" who is a religious icon among the catholic faith... So, I guess if Pete is in fact St Peter (he was an Apostle to God) then all of the above would be rude to religious people. But at least with "Aw, for Pete's sake" it's only a few religious unlike "God" and "Heaven" which can upset all regions and most people won't know that Pete is St Peter so you should be safe. Come to think of this... Whoever started this really didn't like god or faith in general... I'd recommend using it among friends only. This one is best kept out of the work place unless it's a relaxed and casual environment and you know it won't upset anybody.

Someone else gave you the basic answer. I'll just say that although "for god's sake" is a bit more risky than "for pete's sake" it's a far cry from a very rude curse. It's extremely common and you can hear it every day. Yes, religious people might be offended. Most of the rest of the world probably won't be.