Grenade

The grenade is a weapon in Doom 3. "The infantry issue fragmentation grenade is activated by a twist detonator. Fire delay is 3 seconds, with an injury radius of 30 meters."

- PDA description

Combat analysis
The grenade is an explosive weapon, dealing splash damage. Grenades can bounce off walls but will explode on contact with a monster. They can be used in corridors to kill zombies around corners or behind cover. Do not use the grenade at close range, as the explosion can hurt the player. Also, do not cook the grenade for too long, or it will explode in the player's hand, killing him.

Tactical analysis
While grenades are handy for flushing out Z-Secs, it is most useful when thrown directly at an enemy. Imps, vulgars and tentacle commandos will die if hit by one, making it a great alternate to the shotgun if the player does not or can't get close enough to a target for the shotgun to be effective. In addition, it can kill multiple zombies with one explosion. Slow moving enemies such as mancubi are also inviting targets. They can also be used to quickly kill swarms of trites and ticks if the swarm is dense enough and the player is far enough away not to be injured by splash damage.

Though grenades can be tough to aim for the inexperienced, they aren't that hard to aim properly once you get used to them. The longer you cook it, the further you can throw it, and the sooner it will explode after you do. Quickly releasing the fire button and aiming at the ground will allow you to roll the grenades across the ground, while a long cook time and a high angle is best for throwing the grenade over cover to hit Z-Secs. Although difficult to pull off at times, you can also do a mid-angle bounce against a wall to hit monsters behind cover on the opposite side of the wall.

Trivia

 * This weapon has two names in the game: the name of the weapon itself is grenades, but the name of the ammo (which is the weapon itself) is hand grenades.