Pepper gun

The Pepper Gun is a riot control weapon used by security forces. It can stun a target for a few seconds without causing long-term damage. It does not affect MJ-12 Commandos or monsters.

The Pepper Gun is first found near the front of the Statue of Liberty on the first mission. If not obtained there, it can be found in the MJ-12 base in Hong Kong.

Ironically, UNATCO, a so-called peace-keeping organization, almost never issues Pepper Guns.

Tactics
In a pacifist/stealth run, Pepper Spray is useful if you cannot get behind a target and there is an alarm console nearby which means you can't use the tranquilizer darts. The prime example of such location is the Hong Kong police station. Otherwise it's just good at what it does - disabling enemies. If they're close enough, you can disable multiple in a single spray, letting you do deal with them hovewer you see fit, or just run away. Still, it's rather a situational weapon.

It can also be used on certain laser-beam tripwires to bypass them without triggering them: the spray can block the beam without triggering the security device, allowing you to crouch, spray, and slide past undetected. Unfortunately, only a minority of triggers are susceptible to this trick and there's no way to tell which ones without risking setting the trap off.

In-game Description
The pepper gun will accept a number of commercially available riot control agents in cartridge form and disperse them as a fine aerosol mist that can cause blindness or blistering at short-range.

Pistolet pieprzowy