Commonly thought of as the acronym for "oh my god", however it really means "operate my gooch". The person on the receiving end of the remark must then lick, suck, fondle or somehow "operate" on the gooch of the one who made the remark.
Brennan- "Hey! What are you doing? Wanna come over?"
Linda- "I'm playing checkers, what about you?"
Brennan- "OMG. Me too! You should come over and we can play checkers then you can fondle my bacon strip and surrounding area!"