sit on a ham sandwich with mustard!

Only used in the direst of situations, when an extremely rude person is relentlessly insulting you. It is both a powerful offense and defense.

Tommy:'Did you hear what Sarah told Bob? She told him to sit on a ham sandwich with mustard!'
Jessica:'What happened to him?'
Tommy:'His eyes rolled back in his head, his blood fizzed and boiled, and his spine slid out of his anus!'