Often used in first-person shooters, a pz is basically a one shot headshot. Abbreviation for "easy peasy". Pz's are usually achieved through extreme luck or extreme skill.
Player 1: "Put away that usp you're not going to kill me with it"
Player 2: *aims for Player 1's head across the map and fires one round*
Player 2: "Ohhh, pz!"