When one epithet simply will not do, and you don't have time for two. A convenient combination of Shit Head, and Dip Stick, ShitStick is crude enough for all occasions in which either of the other two would have sufficed.
Screaming at your ex for not paying his share of the last electric bill, thereby causing shut off. Yelled back as you leave for the last time: "You ShitStick!" and you're out.