Dirty Camper

You say this towards someone in a jokey disgusted tone when someone is camping in a videogame

 Camping 

Camping is when in shooting games you hide and stay in one position - then just try to kill the people they happen too see, they often use sniper rifles. Campers are bad people... until you do it yourself, which is rather fun.

Origins

This term was created whilst playing Goldeneye 007.