This page is a work in progress please add anything relevant.
The Ammonomicon is an in-game resource for information on guns, items, enemies, and bosses. It can be accessed by going into the game menu and clicking the Ammonomicon tab. On Nintendo Switch, you click minus or plus then scroll down to the Ammonomicon tab and click it to open the Ammonomicon.
Guns[]
Guns are the player's primary method of attacking enemies, and can be found by opening chests, defeating bosses, purchasing them from shops, or receiving them from NPCs. The player can carry an unlimited number of guns. If a gun runs out of ammo it can be thrown by holding shoot.
All guns come in 5 "types":
- Automatic, which automatically fire bullets when holding down the shoot button and generally have large magazine sizes
- Semiautomatic, which can also fire by holding down the shoot button but generally fire faster by tapping it, and have small magazine sizes
- Charged, which need the fire button to be held for a short moment before the release of the projectile (some guns don't need to be charged to shoot, but the uncharged shots deal less damage)
- Beam, which are similar to Automatic, except they fire a continuous beam rather than individual bullets
- Burst, which work like Automatic or Semiautomatic, but fire multiple projectiles and consume multiple ammo in one shot
All starting guns, along with Gunther, Elimentaler, Casey, Dueling Laser, Windgunner, Betrayer's Shield with the 
Betrayer's Lies synergy, and the AKEY-47 with the Akey Breaky synergy have an unlimited amount of ammo, but are unable to break secret walls. All other guns have a limited amount of ammo, enabling them to break secret walls. Additionally, ammo can be replenished by finding ammo pickups.
If a gun is out of ammo, it can be thrown by holding down the fire button and deals 20 damage if it hits an enemy. This damage can be increased by the Ruby Bracelet, which will make the thrown guns explode upon contact with an enemy. Thrown guns can detect secret rooms.
Four guns do not appear in the Ammonomicon (and this list): the Prize Pistol, used in Winchester's game; the Mimic Gun, which can rarely replace any gun and must be used until the player picks up ammo or does enough damage; the High Dragunfire, found only in a special Secret Room; and the Windgunner, which can be temporarily used when Sprun transforms.
All guns, after emptying a clip, will have to reload, which takes a short time, varying with the gun. This time can be reduced, or entirely negated by the Cormorant synergy, If a gun is left unequipped for double the time of its normal reload, it will passively reload.
If the player is too close to a wall and is facing it directly, the gun will not be able to shoot. This prevents loss of ammo by accident in cases which bullets wouldn't hit any enemies by any chance.
If left on the ground, guns will be stolen by the Resourceful Rat. If the player has the Ring of the Resourceful Rat, guns can be traded for a similar-powered item, while having the Resourceful Indeed synergy removes the stealing entirely.
There are currently 243 guns in the game total, including 191 base game guns, 15 guns that were added in the 
update, 15 guns that were added in the 
update, and 22 guns that were added in 
update.
For weapons cut from the game or unused, see here.
Items[]
Items can be found by opening chests, defeating bosses, purchasing them from shops, or receiving them from NPCs. These items can be passive upgrades, active abilities, or single-use consumables.
Most active items recharge as damage is dealt, while others recharge on a timer.
Single use items will stack if multiple are found.
There are currently 271 items in the game total.