When you are so frustrated or annoyed by something that you'd rather die than tolerate another minute of it.
When a loud speaking co-worker who sounds as dumb as a caveman is on phone calls all day and you can't take it anymore. You just want to put yourself out of your misery by shooting yourself in the face...
You may say something under your breath such as "For some reason, I just want to shoot myself in the face".
an expression of self-loathing or disgust directed towards either yourself, others, or an event. Also expressed as "shoot me in the face".
I didn't pass? Shoot me in the face.
He struck out? Shoot me in the face.
I came already? Guess I won't be shooting you in the face. Shoot me in the face.
a sign of disgruntlement over an event
I just broke and fell out of my desk in front of the whole class! I wanna shoot myself in the face!