Quartet Arms

Quartet Arms is the name of the weapons weilded by the four legendary heroes: Yuzusuki from Planeptune, Kuterogi from Lastation, Gheytz from Leanbox, and Miamoato from Lowee. In Hyperdimension Neptunia and Hyperdimension Neptunia Re;Birth1 these weapons serve as the keys to open a path that humans may take to Celestia. For that reason, the weapons were disassembled and scattered across their native lands.

List of Quartet Arms

As the name implies, there are four weapons:

Yuzusuki's Trinity Blade: The 3D shock-waves emitted from the Trinity Blade are said to be able to pierce through the heavens.
Kuterogi's Dual Revolver: The bullets from his revolver are said to be stronger than beast's howl. This gun was used to open the gate in a battle against the goddess.
Gheytz's Wisdom Bow: The giant bow used by Gheytz said to pierce the heavens, much like the Trinity Blade.
Miamoato's Trust Spear: It's widely known that the spear he threw could pierce through any material at an ungodly velocity. The Trust Spear is engraved with the Miamoato Seal of Quality.

The Dual Revolver of Lastation is likely a reference to the DualShock line of controllers for the PlayStation family of consoles.
The "Miamoato Seal of Quality" is a reference to the Official Nintendo Seal, a mark placed upon games, hardware, and merchandise that has been manufactured or officially licensed by Nintendo.