Bow and Arrow

The Bow and Arrow (弓と矢) (more generally the Arrow (矢) as the only component necessary to activate Stands) is a powerful item introduced early in Part IV.

In Part IV, it becomes a major plot-driving force for its role as the source of many new Stand users.

Also in Part IV, it is revealed that its influence extends back to Part III. Some of the Arrows or fragments of Arrow-heads also bear influence on the events of Part V and Part VI; where further previous influence is detailed.

History
There are six known Arrows forged from a meteorite that crashed in Greenland, circa 100,000 BC; although even before then, its properties were known and utilized.

Stand-awakening property
The stone that the meteorite consisted of will catalyze and awaken the Stand of any living creature it cuts.

However, if the target of a cut does not possess sufficient spiritual strength, he/she/it will die from the resultant spiritual strain. On the other hand, the Arrows normally only seek out (and cut) those who can handle the strain to begin with.

One could argue that the arrow-stone meteorite sought out Earth with its many strong spirits, rather than striking the planet by chance.

Other physical effects of piercing
In certain cases, such as with Ken Oyanagi and Stray Cat, with neither of them being exposed to regeneration or regenerative abilities, the wound caused by the arrow will heal and leave a hole about the size of an average coin.

As the origin of Joestar Family Stands
The Arrow's effects are also transferrable down bloodlines, generally without exception as the Arrow that pierced Jonathan's body taken over by Dio awakened Stands in the rest of the Joestar family, with certain people without the necessary spiritual strength suffering from the strain (such as Holy Kujo and Josuke Higashikata).

"Requiem" Stands
When a Stand user is pierced by the Arrow, as in the case with Yoshikage Kira, the Stand doesn't change, but gains a new power; the user changes in appearance as well.

But, if the Arrow hits the Stand instead of the Stand User, the Stand, then known as a Requiem Stand, completely changes form and its powers become much greater.

Breaking an Arrow-head; Fragments
It is possible to break an Arrow and render it ineffective. This is largely implied to be related to the insect-like carving on the flat face of an arrow, which, if intact, will be usable.

It can even retain its effects and seek out potential Stand users in the form of an amulet that Jotaro gave to Jolyne, as long as the insect carving on its face is intact and it is able to pierce its target.

The Arrows
Six Arrows have been found so far. All of them were originally stolen from an excavation team in Egypt by Diavolo and all but one were then sold to Enya Geil when he was 19. They are as follows:

Might be the same arrow which pierced Dio.
 * 1) Possessed by Enya Geil and used to awaken Dio Brando's Stand. May be the source of the shard that Jolyne receives at the beginning of Stone Ocean.
 * 2) Given to the Nijimura brothers' father by Enya. Used by the brothers to create stands and discover one able to kill their father. Later stolen by Akira Otoishi who tried it on two rats, then was taken into Speedwagon Foundation's custody. May be the souce of Jolyne's amulet.
 * 3) Given to Yoshihiro Kira by Enya. He used it to awake his son's stands and years later used to create other users to protect him. Its whereabouts after powering up the Stand Killer Queen with Bites the Dust are unknown, maybe it was destroyed when Yoshihiro's picture exploded.
 * 4) The arrow that Diavolo did not sell to Enya. He gave it to Polpo and became part of Black Sabbath to test new members of Passione. It was shattered with the death of Polpo and Black Sabbath's destruction.
 * 5) Recovered by Polnareff after his fight with Diavolo, able to awake Requiem abilities. Later entered the possession of Giorno Giovanna.
 * 6) Maybe the arrow head given to Enrico Pucci by Dio himself, though its whereabouts are unknown, since it seemingly disappeared (or returned somehow to Dio) after Pucci was pierced.

People shot with the Bow & Arrow
By Enya Geil: By Keicho Nijimura: By Akira Otoishi: By Yoshihiro Kira: By Jolyne's amulet: By Pucci's piece:
 * Dio Brando
 * Anjuro Katagiri
 * Tamami Kobayashi
 * Toshikazu Hazamada
 * Yukako Yamagishi
 * Akira Otoishi
 * Koichi Hirose
 * Mushikuidenai
 * Mushikui
 * Yoshikage Kira
 * Ken Oyanagi
 * Mikitaka Hazekura
 * Yuuya Fungami
 * Toyohiro Kanedaichi
 * Terunosuke Miyamoto
 * Jolyne Cujoh
 * Hermes Costello
 * Enrico Pucci
 * Weather Report

Steel Ball Run
A similar case happens in the alternate universe, in a desert along the trail of the Steel Ball Run.

In this case, a meteorite crashes into the desert and forms a mobile formation of land known as the "Devil's Palm" that would change location every time and was feared by the natives near the area.

As was the case with the Arrow, it was rumored that the "Devil's Palm" sought out future stand users, and like the arrow, imposed a heavy affliction upon them from which the person would survive and obtain a Stand.

JoJolion
After the 2011 Tohoku Earthquake, the Wall Eyes sprout up in locations corresponding to the Stand users.