Flare

Flares are throwable light sources that have to be lit first and glow reddish for about 60 seconds. They can also be used as ammunition for the flare gun.

A maximum of 10 flares can be held in the inventory.

Gameplay
Flares are a very useful in the caves, as they emit more light than the lighter and can be thrown away to distract and scare cannibals. They don't work underwater and thrown flares can't be picked up again.

As a light source they're somewhat inferior compared to the lighter and flashlight, which are held in the left hand and can be used while climbing and fighting.

Flares, up to 10 at once, can be combined with the flare gun to be stocked as ammunition. When shot with the flare gun, they can burn creatures, flora and bodies. To tell how much ammo you have, place your cursor over the flare gun, it will reveal your ammo amount. As you can stack 10,000 flare gun ammo, surplus flares should be used for ammo if found.

When thrown, a lit flare has a burn time of 60 seconds, during which time it will emit light. When held in the player's hand, a lit flare will burn indefinitely.

Trivia

 * As of v0.62, loose flares have been removed from the game. They can now only be found in or openable yellow crates or destructible crates.
 * Before v0.65 flares had no animation and were lit directly, which made them easier to use in emergencies.
 * A bug allows lit flare that has not been thrown to be placed back into your inventory and it can be reused, as if it had not been lit.