(last updated: 12/28/17)Going along with the ability of energy to influence an area or body, many items exist in the world that have been charged with the natural energy throughout the world or crafted with techniques that work the understanding of the martial arts into their composition. Many ancient devices that have explicitly been lost to time, such as the Ame no Nuhoko or the Lance of Longinus, tend to be actual, real items with bizarre powers and properties.
It goes without saying that some of these contrivances of history are martial arts techniques or other abstractions that gained their own legend, much as how the Sword of Kusanagi was actually history's way of representing the bloodline of the Kusanagi clan. However, items that are beyond the norm may have been produced supernaturally.
Most of the time, a metanatural item occurs accidentally--items that have survived through extraordinary circumstances tend to have bizarre properties. However, certain groups and individuals have the ability to create such items with effort. Many ancient swordsmiths were able to do so naturally, and an actual Masamune blade may be one of the strongest swords in existence.
More recently, the state of technology has advanced such that it can just barely scratch the surface of metanatural properties, and certain very specific megacorporations and cartels are able to replicate metanatural effects in their machines and weapons. Some have even dabbled with cybernetics, creating machines that are able to channel chi natively. This is a hot-button topic amongst the government and fighting communities, making these machines exceedingly rare.
However, what doesn't seem to change about any specially-created item is that it requires a commensurate skill to use; automata require complicated power sources and decision engines, and may not be entirely artificial, while a sword or gun is only going to be as powerful as the hand that wields it. This limitation means a novice is incapable of wielding godlike power, and is only the barest hint as to the danger that these weapons and items present to the world..