All enemies in the game can drop charms, they are extremely rare! There are 7 different charms and they give a passive boost for the player by just having them in your inventory. They can be dropped if you die.
All monsters can drop Pets. There are 3 different types of pets, each more rare than the other. If the player dies the pet has a 50% of dying as well. Pets are also very rare.
There are also very rare capes that can be dropped by all monsters in the game.