It is "God almighty!" "Cod almighty" is playing with words as a joke. Yes, it is an exclamation of surprise and/or irritation. It has the same meaning as "My goodness!" or "That's enough!"
"You're late! God almighty! I've been out here freezing for two hours!"
"God almighty, you scared me! Don't sneak up behind me like that!"
It should be noted here that saying "God almighty" is considered by the most conservative Christians as "taking the Lord's name in vain." However, I've never heard anyone get mad about this.