Flare gun (Fallout 4)

The flare gun is a weapon

Gameplay
The flare gun is a break-action single-shot weapon that is not designed to deal direct damage, but instead to summon nearby Minutemen for assistance using flares. It can also attract nearby Brotherhood of Steel vertibirds. Firing a flare directly at an enemy will cause a small amount of damage, but virtually every other weapon will yield better results in the heat of battle.

The flare gun is unmodifiable, as its purpose is to signal the Minutemen for assistance. It is poorly suited for lighting dark areas as the flare does not stick to surfaces and has a time delay ignition.

Location
The Sole Survivor is given the flare gun by Preston Garvey after completing the quest The First Step for the Commonwealth Minutemen.