https://wiki.teamfortress.com/wiki/Jarate

Jarate, the "Jar-based Karate", is an unlockable secondary weapon for the Sniper. It is a standard glass mason jar filled above half-way with the Sniper's urine, capped with a screw-on lid. In the Festive version, the jar is replaced with a corked glass bottle, labeled with a holiday-themed sticker upon which "Merry Smissmas Mate!" is written in cursive font, and the bottleneck wrapped with a team-colored bow.

The item is a thrown weapon; the jar breaks and the liquid is splashed over a short distance, either upon immediate contact with the world or another player. Enemies caught within the 200 Hammer units splash radius are soaked in the contents of the jar for 10 seconds (5 seconds on a target continuously healed, for example by a Medic's Medi Gun, the Amputator's taunt, or a Dispenser). During this period, all incoming damage is registered as Mini-Crits. The victim's view is tinted a watery yellow, and they shed yellow droplet particle effects.