Skull symbol
Though not officially named, it seems to be an important tool for Shinigami during missions in the real world. It can basically force out one's spirit from a human body or a Gigai (see also below), a human soul or an artificial one alike (see also below).
Hell Butterfly
Main article: Hell Butterfly Hell Butterflies are completely black butterflies that serve various purposes. They guide the Shinigami through the Senkaimon when travelling between the Soul Society and the Human World, thereby saving them from the inconvenience of passing through the Dangai Precipice World. Hell Butterflies are also used as messengers between Shinigami, often carrying important orders. It is implied that Hell Butterflies are bred and taken care of by Shinigami in Seireitei, the latter task being carried out usually by new and inexperienced members of the Gotei 13. Hell Butterflies, like the Shinigami themselves, are only visible to spiritually aware beings.
Gigai
Main article: Gigai In certain circumstances, a Shinigami will need a way to stay in the human world for long periods of time, interact with the living, and/or recover their powers when the need arises, all of which they cannot do in spirit form. Thus, the Gigai was developed.
Artificial souls
A large amount of newly manufactured Soul Candies
Artificial souls, as the name suggests, are souls designed by Shinigami scientists to separate a Shinigami's spirit from a Gigai, should they be inhabiting one, or to evict stubborn spirits from their corpses if necessary. It is commonly called Soul Candy, as the Shinigami Women's Association complained that the name "Artificial Soul" was not cute and had it changed.
Modified souls
Modified souls are artificial souls designed to enhance regular human physiology, making them capable of battling Hollows equally. The modsouls are condensed into tiny, candy-like orbs and placed into corpses to achieve their function as soldiers to combat Hollows. They are also more independent to fit with their purpose. The mod souls were exterminated after the experiment was halted due to ethical reasons, since they were intended to be used to reanimate human corpses to use as weapons against the Hollows.
Memory replacement
In some cases, a human witnesses a Shinigami purify a Hollow or affect his surroundings in a significant way. To keep the incident a secret, Shinigami perform memory replacement with an item called Kikanshinki (記換神機). When used, a bird's head pops from the top of the device and produces a puff of smoke. The human it is used on is knocked unconscious and wakes up a while later with a new memory. However, the new memory that the human acquires is random and often based on the limits of what they themselves will believe.
Soul phone
A vital tool for any Shinigami stationed in the real world, this variation on a cell phone functions both as a regular phone and as a communication line with the Soul Society. It receives information about the time and exact location of a Hollow's emergence via a Global Positioning System (GPS). A Shinigami's kills are also recorded in the phone and can be used as currency (according to the bounty placed on each Hollow).