Flashlight

The  is a valuable source of light.

One Late Night
The can only be acquired from Robert from the spirit realm. It comes without batteries, but requires 4 of them to work. The is necessary to defend oneself from the Black Widow by shining the beam directly onto her.

One Late Night: Deadline
The only available is via Robert's smartphone found later in the game. The is necessary to not only defend against the Black Widow, but also the Shadow Creatures wandering all over Delta 5. The smartphone doesn't require any batteries and therefore can be used without limit.