Flashlight

The flashlight is a weapon in Doom 3. Its main purpose is to light up dark corridors in the original game, although it can be used as a club at close range. "UAC Standard issue light source. This model utilizes a static transfer power supply, so battery replacement is unnecessary."

- PDA description

Analysis
"Power fluctuations and maintenance issues continue to create poor lighting at the UAC Facility and flashlights are now required for all security forces. Also works as a club in close combat."

- Doom 3 instruction manual

The flashlight in starter levels can be used to attack zombies to conserve ammo. It has slightly shorter range than the fists when used in this way, but is about twice as powerful. Attacking an enemy stronger than an Imp is not recommended. In later levels, the flashlight should be used to light up dark corridors only. Upon sight of an enemy, a more powerful weapon should be swapped out. The flashlight could also be used to attack corpses on the ground to check that it is dead so that it does not rise again as a zombie. Additionally, if a zombie is dormant in this way, it can be alerted to your presence by shining your flashlight at it from a distance, allowing you to deal with it safely from a distance. In deathmatch, using the flashlight alerts other people to your whereabouts. The weapon is not included in the Xbox version's deathmatches.

Trivia

 * The Doomguy's inability to attach his flashlight to a weapon in the game, commonly known as "There's no duct-tape on Mars" problem, is often a subject of parody. This led to creation of the Duct Tape mod and its various successors. The aforementioned BFG Edition of Doom 3 and its later releases incorporated the armor-mounted flashlight by default.