— The Postal Dude
"Press r to unzip your pants. Press it again to zip your pants back up. When you unzip your pants, both hands will be… occupied, so you can’t hold a weapon with your pants unzipped. Press fire to urinate. If the ammo number listed by the picture of the zipper is 0, you’re out of urine. Wait a few moments, and the Postal Dude will muster up some more liquids. Walking around with your pants down in public will cause police to arrest you and general bystanders to mock you." — Piss's description in the manual
If the Postal Dude unzips his pants and pisses in a victim's mouth, they will start vomiting for a few seconds and then run away in terror. Unlike weapons, piss cannot kill, and instead its main use is to distract enemies for a few seconds, allowing for a quick getaway. Later enemies will not vomit if pissed on, but will still be distracted by it. In the Enhanced game mode (awarded for beating the game), the Postal Dude can piss napalm, which sets people on fire. Another use of piss is to put out fires, be it from the environment or the Postal Dude himself. If the Dude urinates above his head when he is on fire, the fire will be extinguished instantly. If he urinates above his head when he isn't for a moment, the Dude will cough in disgust after a few seconds.
One of the errands on Wednesday is to go to piss on the Postal Dude's father's tomb at the Cemetery. On Friday, the Postal Dude wants to take a "wicked leak" since the beginning of the day. When he does so, his piss will appear green and slowly get hurt while urinating. He then adds a new errand, which is going to the Clinic to get cured. At the clinic, nurses tell him he has gonorrhea and that he needs to go to see Vend-A-Cure, a machine that will give him Gonorrhea Medicine after getting some piss samples from the Dude. This errand is optional, depending on whether the player makes the Dude piss or not.
The Postal Dude can again piss in Postal III. It has the same function as in Postal 2. It also features a secondary fire which forks the Dude's stream of piss, at the cost of emptying his bladder at a higher rate.
- Peeing on Mike J causes him to begin dancing and music to start playing.
- In Postal 2 Complete, Enhanced Mode also grants the ability to switch between several liquids with alternate fire, including fire, blood, gonorrhea, puke, and gasoline. Since pee regenerates, this makes the fire piss an extremely useful weapon.
- If the Dude pisses on someone on Friday before taking the Gonorrhea Medicine, they will vomit no matter where they are pissed on, and they will continue to vomit as long as the Dude pisses on them. The same goes for puke piss in Enhanced Mode.
- The Postal series are one of the only games that allow you to piss anywhere.
- When the Postal Dude is at low health, he'll start pissing blood.
- Urinating on yourself gives you the achievement "It's Sterile and I Like the Taste" in the online versions of Postal 2.