
For Christ’s, God’s, goodness’, heaven’s, pity’s, etc. sake
Emotional Intensity
The phrase adds strong emotion to a plea or complaint, often out of desperation or exasperation. 
Not Literal
It's used figuratively and doesn't involve a literal appeal to the sacred. 
Possible Offense
Some listeners may find versions with religious references (e.g. God's, Christ's) offensive. 