Vorpal Sword

Cannot be auctioned, traded, bazaared, or delivered.
Cannot be obtained as a random reward from the Gobbie Mystery Box Special Dial and similar sources.

The Vorpal Sword appeared in the original Final Fantasy for the NES. It was equippable by the Warrior, Thief, Red Mage, Knight, Ninja, and Red Wizard classes.

The "vorpal sword" was the sword mentioned in Lewis Carroll's poem "Jabberwocky" (from the book Through the Looking-Glass), and was used by the hero of the poem to decapitate the Jabberwock. According to the poem, it made a "snicker-snack" noise when used.

Carroll's "nonsense" words were often made up of 2 words spliced together, like "frumious" from "fuming" and "furious", so "vorpal" is likely the same (though he never mentioned which two, "voracious" springs to mind as one).