The Longinus
Created by a stranger, the Longinus is an armory containing celestial weapons or, at least, super-powerful like the legendary swords Dawnbreaker, Durandal, Caliburn or Mistiltein but also guns like Ebony and Ivory. But in reality, it would contain more than conventional weapons. The best example is still to quote some of these weapons like Divine Dividing and Boosted Gear. This example shows that the Longinus is more an inventory list than an armory literally because it could also house creatures considered as living weapons.