The flashlight is an accessory in S.T.A.L.K.E.R. games. It is a headlamp strapped to the head. It illuminates a small area giving a workable view in the midst of darkness. It can be toggled on/off by using the 'L' key (default, can be configured).
The flashlight is available on all armors and invaluable in night time operations, though it does reveal the location of the wearer. The flashlight has an unlimited amount of energy and shines without any problems. A downside is that NPCs will spot the player more easily if they have their flashlight in use, making the use of Night vision advisable as well.
In addition of the player, NPCs will equip flashlights at night between 10PM and 6AM, and in underground levels. Interestingly, the flashlights never appear on NPCs until used. NPCs automatically turn their flashlights off during combat.