Fuckin A
Fucking Amen, as in agreement with a statement. However, the speaker will not say the Amen part fully as not to blaspheme against God. Stupid teenagers will someones use it in a derogatory sense as a way of saying "fucking asshole" but teenagers are stupid as hell.
"Dude this pancake is the shit."
"Fuckin A dude."

- See also the Big Lebowski