WoWDB

EDIT:  Since level scaling was expanded to include old content with Patch 7.3.5, items that previously could not drop or had an extremely small pool of mobs to drop from are now being looted again by players.  die_twissis on /r/woweconomy posted proof (direct link, not in English though).

An extremely low drop from Uldaman dungeon creatures. May still be in the game, but I really doubt it still drops. Even if you exclude WoWDB (which is silly, but whatever) due to its young age as a database, Wowhead does not list any source for the item - even though it used to have such a list prior to Cataclysm. The single Wowhead comment claiming that he/she looted it post-Shattering is dubious when considering the claim dates it to Patch 5.1 when the comment was posted two entire patches later (in Patch 5.3.0).

This item is/was the only fez in the game with a solid red color. If you do happen to spot it in the Auction House, expect to pay a really really pretty gold coin for it if the seller knows its true value.