I don't have the rarest of the rare items but I have a few that are no longer in the game and quite cool, as well as Tyrannical Cloak which can be used on anything as far as I'm aware.
Will be done using the well known transmog exploit. PM me on here and we'll discuss prices etc.
Horde Items:
Unmelting Ice Girdle - Unmelting Ice Girdle - Item - World of Warcraft
Benediction / Anathema - Benediction - Item - World of Warcraft - Anathema - Item - World of Warcraft
Level 60 Zin'rokh Destroyer of Worlds - Zin'rokh, Destroyer of Worlds - Item - World of Warcraft
Rogue Tier 3 - Shoulders / Boots / Belt - Bonescythe Pauldrons - Item - World of Warcraft / Bonescythe Sabatons - Item - World of Warcraft / Bonescythe Waistguard - Item - World of Warcraft
Alliance Items:
Tyrannical Gladiator's Greatcloak - Tyrannical Gladiator's Greatcloak - Item - World of Warcraft