Excalibur

The sword which Cora and David found in the secret basement of the Redmond Community Hospital has been identified by Doctor Raven as Excalibur.  The Excalibur.  Cora used the sword against the Horror during that battle, and has been carrying it since, strapped to her back under her coat.  The sword's true name actually means "Purifier" ("Excalibur" is an altered version of its common name Caladbolg, or "Hard lightning".)

It originally appeared as a fairly rusty, antique blade.  Almost as soon as Cora took possession of it, the sword's appearance started changing, becoming more Amerindian.

When Cora used it for the second time, going against Dr. McCoy-turned-demon, the sword spoke in her with a woman's voice, and guided her actions through the fight.  The sword is mundane against non-Awakened target, but deals tremendous damage to Awakened or magical targets.  Cora has been practicing assiduously with it.  As time passed and Cora bonded with the weapon focus, it has became virtually invisible to mundane detection unless she draws it.