I just vendored about a bag's worth of old gear (including all my hot Mara NR gear) a few days ago, so you def have me beat. But I think I'm a contender for most old/useless stuff.
Some gems include:
* the Arcanist Crown is my official FR helm. And of course, Flarecore Mantle for my shoulders.
* 2 gemstones and the seal of ascension for my UBRS key -- never completed.
* 4 chapters of Draconic for dummies -- because, you know, i might finish it someday.
* 5 scarlet thread and abom stitchings -- just in case the carapace drops from the Beast and I can make my Cap of the Scarlet Savant.
* Skin of Shadow -- in case i need to get another Libram of Focus to enchant my head/legs
* 2 Zandalar Honor Tokens -- because i might need a zanza pot?