Chests can be found all through the gungeon and usually drop Consumables, Passive Items, or Guns. Most chests are locked and the player must use a Key, which can either be dropped in a room, or obtained from an NPC (such as the Shopkeeper), in order to unlock them. Unlocked chests, though much rarer, can also be found throughout the gungeon.
Chests can also be destroyed in order to obtain loot of considerably lower value. This is accomplished by shooting the chest until it explodes. In most cases, you'll be given Junk.
Note: Chests found in treasure rooms will always be locked.
The following is a list of the different kinds of chests, in ascending order of rarity:
A Glitch Chest appears to be flickering and changing chests every so often.
Opening a Glitch Chest will cause the player to teleport directly to a mimic of the next floor, however there will only be one door, towards the boss room which will contain glitched Beholsters. Defeating the bosses yield the normal loot for that floor, plus 7 guns and other consumables.
Rainbow Chests are extremely rare, dropping anywhere from 7-9 items and/or guns.
Mimics are chests that attack the player when they attempt to open it, the loot from the chest can be received once the mimic is killed, a mimic looks exactly like any other chest, to prevent chest ambushing, shoot the chest 3 times, the mimic will move, it will not move if the chest is not a mimic.