The flashlight is an in-game item given to the player in Tattletail.
The flashlight is a large flashlight that, instead of using standard batteries, uses magnetic induction to build electricity. When the player first receives it, it glows green, but from then on it glows white.
The player receives the flashlight on December 21, 1998. It is used to see in the dark when the lights are out.
Tattletail is afraid of the dark, and will emit noise when in the dark too long. The Flashlight counters this.
The player must shake the flashlight by holding the right mouse button in order to power it up. However, this creates noise, and will attract Mama to the player. Looking at Mama directly will cause the flashlight to go out.