Mine is:
•Benediction staff
•Competitor’s Tabard
•Some Zul’gurub gear pre cata
•PvP titles from vanilla knight and knight-champion
•Heirloom from MoP
Did forget to mention the cute “baby blizzard bear” 
I guess I have more stuff but nothing special 
How about you?
If interested here is my collection:
https://worldofwarcraft.com/en-gb/character/eu/kazzak/qrazie
A bunch of the trade card game code items - tabards, mounts, etc. I also have the Wrath launch event gear from when I earned it. I have the old Mountain Dew promotional stuff too.
Most rare item would be my sanity
My three unused spectral tigers, probably.
Although I do have some pretty obscure items and achievements.
WoW that rare and worth plenty today!
I have a night elf head in one of my toons banks, despite the character now being Alliance because I race-changed a Vanilla toon who was always in AV.
Nothing particularly rare, perse, but I did keep Shadow’s Edge, Deathbringer’s Will and the Quel’Delar on my DK, all gotten when Wrath was current. Just couldn’t bring myself to sell all that, so they’re chilling in my bank.
Now that’d be an awkward conversation with the bank teller.
Let’s just say I don’t support what Sylvannas did, but it solved a lot of my problems.
Check my profile if you care. I don’t have the energy to list all the rare stuff I have.
Ghastly Charger’s Skull tcg mount
Super Simian Sphere
Necromedes, the Death Resonator
Chromatic Sword
Idol of the Raven Goddess
I have seen that drop once and I didn’t know what it was. I told my old buddy at the time “You take it. I am sure I will find another.”
I’ve got gladiator mounts, old PvP tabards, CM sets, TCG mounts and tabards and a bunch of other removed items, but the rarest thing I still have is probably the elite thrown weapon from s9 in my rogues bank.
It’s a grey item now since they removed the ranged slot from rogues, but it used to be a real item and the 2200 version even had its own appearance that differed from the standard throwing axe from that season. I doubt anyone really saved theirs since not only did transmog not exist yet, but you couldn’t transmog them anyway. I would imagine basically everyone that had one vendored it when they got the next seasons item. Dunno why I stuck mine in my bank, but its there.
I’d love to see if someone has the elite appearances from the Cata elite wands, I dunno if they had unique appearances too, but wands weren’t transmoggable for many years after Cata so it’d be interesting to see if anyone kept theirs and could use it now (assuming there were wands to transmog to)
Black Dragonflight Molt - Item - Classic World of Warcraft (wowhead.com)
I still have this thing on my retail hunter and a few other odd removed useless quest items.
I think I’m the only person in the world with 14 Crowns of the Fire Festival on one character.
back in my wotlk days i would play like 12 hours a day i seen it drop once back then and lost the roll then i started farming for it my self too expansions later i got it to drop again
That throw me back in time. I still have quiver and Thorium Headed Arrow in the bag 
+ poison for the rogue!
What can I say, I’m a lucky man.
Brewfest Ram is about it.
I have some tabards from past events like the Scourge Invasion but they may not qualify as rare like the ram.
Prestigious Bloodforged Courser.