The Pistol is the default firearm and first weapon received in I Am Alive. This is the only firearm that any sort of non-playable characters uses, so 1-3 bullets can be acquired at a time. This weapon is also required to save some victims, such as the girl handcuffed to a bench. When dealing with multiple gun-wielding enemies, take one out with a surprise kill, then finish the other ones off with the Pistol, Bow, and Machete together for effective means. Using the pistol to tell gang members to step back with the pistol to kill them with the environment also proves to be effective. If they discover your pistol is empty by taking too long to fire or firing it with no ammo, the surprise is lost and they will attack you.
The Bow is the second weapon received in I Am Alive. It is given to the protagonist by Henry as a gift for bringing Mei to him. It uses arrows, which are extremely rare, although they are retrievable after use. This weapon will not intimidate enemies unless the arrow is pulled completely back. The more arrows the protagonist has, the better his proficiency with the weapon is.
The Shotgun is the second firearm and last weapon received in I Am Alive. It is given to the protagonist upon helping a strange man in the dust by providing him with various types of food. It comes loaded with five shells, can instantly kill enemies, and is a better weapon to surprise and threaten with than the pistol or bow, but since nobody else in the game uses it, these shells are all you have in terms of ammo, you cannot acquire or find any more throughout the game. Use them strictly as a final resort, like if you're outnumbered, about to die or if none of your other weapons have ammo.
The Machete is the only melee weapon in I Am Alive. It is received by the protagonist after he kills his first enemy in Chapter 1: Return. It is the basic way to begin and end battles and can also help deal with other machete wielding enemies. It should not be used at all against a firearm wielding enemy unless a surprise kill is done.