Uniques
From DoomRL Wiki
Uniques are special one-of-a-kind weapons/armor that can be found throughout the game. Don't expect to find more than one or two per game, unless you play Angel of 100. They are similar to Exotics, but the latter can exist in multiple copies.
As of 0.9.9, some uniques are now able to be modified. Those that are will have an entry that tells you how many mods can be fitted on a given unique.
As of 0.9.9.1, Uniques cannot be destroyed.
