GJC
God Jesus Christ! Similar to OMG (Oh my God!) but more powerful in meaning for the reason that it contains more names of a higher deity.
Jim: OMG! You'll never guess what just happened!
John: *sigh*...what?
Compared to:
Jim: GJC! You'll never guess what just happened!
John: WHAT WHAT WHAT!?!?!
John: *sigh*...what?
Compared to:
Jim: GJC! You'll never guess what just happened!
John: WHAT WHAT WHAT!?!?!