Red XIII's ultimate weapon within “Final Fantasy VII” is known as Limited Moon. Red's weapons are headdresses due to him being a canine variety of animal. This headdress is the ultimate weapon for the character, and can only be obtained at a certain point within the game, in disk 3.
In order to obtain this rare piece of headware, the player must trabel to Cosmo Canyon in disk 3, the home town of Red XIII. Here, with Red XIII in the party, the player can speak to the old Bugenhagen. After some dialogue with him, the player will obtain Red XIII's Limited Moon ultimate weapon.
While this is a powerful weapon, it is quite strange in some ways. The special attribute that determines the weapon's power depends on Red XIII's MP. The more MP he has, the higher the damage, meaning as his MP gets lower, whether from using Materia in battle or having his MP stolen, Red's damage will be lessened.
This leads players to believe that Red XIII should be used as a strictly physical character, not relying on Materia of any kind other than Command or Support Materia. If Red XIII were to play the role of mage in battle, his attack damage would be severely dampened, leaving him vulnerable in many physical aspects of the fight.
This weapon also provides extra hassle for the player, due to the fact that in order to increase Red XIII's power again, he must be given an Ether or other MP restoring item. This is harder to come by than a simple potion for certain more HP = more damage weapons such as Cloud's Ultima Weapon, however in the same respect, a character may be less likely to lose MP in battle, whereas losing HP is almost assured.