Gold Experience Requiem

Gold Experience Requiem (ゴールド・エクスペリエンス・レクイエム) is a Stand belonging to Giorno Giovanna, featured in Part V: Vento Aureo.

This Stand is the evolved form of Gold Experience, created when pierced by the Stand-creating Arrow.

Appearance
Gold Experience Requiem is a humanoid Stand of a height and build similar to Giorno's.

When it first appears, it wears the Arrow on its forehead; which eventually falls to the ground.

Personality
Gold Experience Requiem speaks to Diavolo in the space/time normally occupied only by him and his Stand King Crimson; explaining that it is able to operate independent of Giorno's consciousness.

Like Gold Experience, its lengthy Stand Cry is "Muda muda muda...!"

Abilities
Nullification of Cause and Effect: Gold Experience Requiem's ability is to turn anything, including his opponent's attack and willpower, back to the state of "zero". Hence, it is near invincible, as all "supposed" actions created by an opponent would have been reset (back to point zero). It is mentioned by Giorno himself that he is unsure of the exact workings and limits of Requiem's powers, but it has been shown that its range of influence extends from finger beams, surface contact, and to even being in the mere attention of Requiem.

Requiem's abilities is seen by some fans to be opposite King Crimson's: King Crimson erases the "cause" and keeps the "effect" (i.e time where a bullet would hit him is erased, causing the bullet to warp past him), while Requiem keeps the "cause" but erases the "effect", causing endless scenarios where actions and initiatives are started, but the effects of such does not occur (as shown when Requiem completely halted King Crimson's cause erasing ability).

If the opponent is "killed" by the stand itself, then they will also continuously experience death, as they will die but repeatedly return to point "zero" (i.e Diavolo's endless death loops).

This ability renders Giorno essentially untouchable by anything that would try to hurt him and is perhaps the strongest defense in the series.

Original Abilities: It is often disputed whether Giorno retained his original life giving abilities after evolving into Gold Experience Requiem. After fusing with the arrow, Giorno breaks a column and a piece of it turns into a scorpion that then attacks Diavolo, so it is very likely he still has all of his original stand's abilities.

All-Star Battle
(The information below derives from videogame. As such, it may or may not be considered canon.)

In All-Star Battle, it is shown that Gold Experience Requiem functions normally under the time-accelerating effect of Made in Heaven, and that Giorno remains immune to the effect as long as he has Requiem active; while other characters are severely slowed down.

Trivia

 * After the Stand's first appearance, the Arrow tip falls from its head; leaving ambiguity as to whether Giorno has retained it.
 * Silver Chariot loses its Arrow but remained in its "Requiem" form, possibly due to Polnareff's physical death. As such, it seems likelier that Gold Experience retains its Requiem form after defeating Diavolo, as Giorno is still alive.
 * In the novel Purple Haze Feedback, Giorno uses Gold Experience Requiem to heal Fugo without Fugo noticing.
 * While it is dubious whether the events of All-Star Battle should be considered canon, the fact that GER can negate the effect of Made in Heaven lends some credibility to the fan theory that Giorno might have managed to accomplish the same feat in the manga; and as a result could exist somewhere beyond both occasions that the universe is reset (and/or in the alternate continuity that started with Steel Ball Run), like Emporio Alnino.
 * There is an interesting parallel between Giorno, with Golden Experience Requiem's "state zero" ability, and his father, Dio Brando. Golden Experience Requiem's ability essentially gives Giorno a pseudo-immortality, where Giorno can survive nearly any attack, but most likely has no effect on the regular aging process. This is very similar to Dio, who acquired near-immortality by becoming a vampire.
 * On a side note, could GER possibly prevent aging and render Giorno truly immortal?