Chainsaw/Doom 3

The chainsaw is an extremely powerful close-quarters combat weapon, sent to t Mars Base by mistake from Mixom Corporation. Jackhammers were supposed to be sent in place of them. It's the game's most powerful non-projectile weapon, so watch out for Chainsaw Zombies.

You can find your first one in Service Room 2A of Communications Transfer.

If you're ever completely out of ammo, this is your next best bet at surviving. The weapon is great for zombies since you won't be using any ammo with it.

You can expect damage from larger enemies since you have to be practically on the enemy to use it. It's a last resort weapon, but definitely better than the fists or flashlight.