I know this hasnt been discussed before because I searched for a weapon limit and nothing came up.
BUT, I beleive that it would add alot of role play and mystery to the game if the most powerful weapons were kept at a limit.
In a few other games, once an ultimate weapon or technique is discovered, everyone does their most to acheive that, and soon everyone has the same stuff and abilities.
So if there is a very good sword of excaliber caliber (sorry, no pun intended), there should only be about 10 or 20 of them. If a weaponsmith has the ability to make them, then limit one of the resources required for the weapon, such as a rare jem. If such a weapon happens to be destroyed, then that jem will respawn to a random location.
This can also apply to powerful artifacts or armor.
(Note for the stupid: This is not intended for every weapon)