Rip your head off and shit down your neck 

As can be gathered from the expression, it indicates a state of intense anger and annoyance, so much so that the person making the threat is ready, willing and able to inflict physical pain and degradation upon the person who has annoyed them. While it may not literally result in the removal of the offenders head and defecating into the stump, it will usually result in physical violence and a humbling of the person who caused the offence.
The expression that is believed to have originated with the British Royal Navy. It gradually became used within all branches of the armed forces and later spread to the civilian organisations associated with them before obtaining wider usage.

"Malcolm if you don't fuck off I'm going to rip your head off and shit down your neck!"

Rip your head off and shit down your neck by AKACroatalin March 19, 2015

I'll rip your head off and shit down your neck

A person, or entity, seperates your head from your body and thereafter takes a dumb that glides down your neck.

From the Duke Nukem game, said by Duke Nukem (ingame character).

I'll rip your head off and shit down your neck!

I'll rip your head off and shit down your neck by Nicolai Thomsen January 25, 2009

rip off your head and shit down your neck 

A quote from Stanley Kubrick's "Full Metal Jacket" (1987)

"You know that one quote you always hear in hardcore songs? 'rip off your head and shit down your neck', it's from Full Metal Jacket, a movie by Stanley Kubrick"

rip off your head and shit down your neck by Nekir January 7, 2012