Tusk

Tusk (牙 (タスク)) is a stand ability featured in Part VII: Steel Ball Run. Similarly to Echoes from Part IV: Diamond is Unbreakable, Tusk evolves into various forms.

Ability
In his first form, Tusk gives Johnny the ability to "spin" his fingernails at high speeds and use them as projectiles. Once Johnny shoots a fingernail, it grows back extremely fast.
 * Quick-Spin Nails

Ability
Once Johnny learns to spin the fingernails with aureal rotation, thus bringing Tusk to his second form, he can make the holes he produces move: if for example he shoots and produces a hole on a table, he can move the hole on the surface of the table and whatever touches the table's surface. However, the hole leaves a track behind it as it moves. When Johnny shoots a fingernail with aureal rotation, the fingernail takes several minutes to grow back; however, Johnny discovers that by munching herbs or drinking tea he can accelerate the growing process.
 * Ten-Aureal Nails

Ability
During the fight against the stand Civil War, Johnny, in a moment of deep crisis, sees Jesus, who gives him the hint that leads him to discover the third form of Tusk. By shooting himself with a fingernail spinning with aureal rotation, he's able to send a part of his body through the hole, moving it away from his body. This way he can shoot fingernails from different directions, sending his hands or fingers through the holes.
 * Through The Hole

Ability
Tusk evolved once more when Johnny Joestar finally learned how to spin the steel ball from Gyro Zeppeli.
 * Infinite Rotation

After learning how to spin a steel ball, Tusk has the ability to, when it hits a person, insert the spinning motion into the victim, making them spin internally. That spin goes on forever and never leaves the person and his/her stand, forcing him/her to return to the place where he/she was hit, or its equivalent in each parallel dimension. Tusk can  move through D4C's Love Train & stopped time to attack it's enemies. The spin is also transferable between objects, as the Diego Brando from another universe cut his leg off and threw it to Johnny, transferring the infinite rotation to its user.Another example is when Funny Valentine went into a passing car trying to run away from Tusk, the infinite rotation nearly instantly destroyed it, coming back to Valentine.

In the moment that Johnny used the Infinite Rotation with the aid of his horse, ACT 4 was activated, and this seem to have unlocked it, as Johhny can freely uses it even while not using the velocity of a horsey. It can be inferred that he can use as well all ACT's of Tusk, much like Koichi, at any moment.

This ability is likely to be a reference to the Fleetwood Mac song Landslide, as the lyrics suggest the fate of Funny Valentine when experiencing Tusk 4.

Interestingly, ACT 4 punches while making the Kujo family's "ORA ORA ORA" battle cry.

Trivia

 * Tusk (Act 4) is the first stand to have a battle cry in Part VII. This is especially unique due to most of the stands in Part VII being tools rather than humanoids. The second being The World.
 * On occasions Tusk's kanji is written as "爪" (Nail), rather than "牙" (Tusk).