Stacked Items
Stacked Items are items that are illegally stacked, generally consisting of tools, armor and weapons. Back in 2021, these could be obtained using the Crafting Table Dupe.

History
editEarly or Mid 2021
editCrafting Table Dupe was added, which allowed illegal stacked items to be created.
This also included totems, and for a period of time, PvPs were practically infinite. However, this was eventually patched.
Mid 2021
editCrafting Table Dupe got heavily nerfed, then a few days later the change got reverted (exact date unknown).
It should be clarified that also, on an unknown date, stacked tools, weapons and armor got patched. Almost everything except shulkers.
Present
editAs of 2026, stacked items no longer exist and are not possible due to plugins like AEF.