There has been lots of discussion on here recently about if they should or should not bring back old cosmetics. This isnt asking or advocating either way.
But one thing that never gets brought up is what removed transmog or mounts people would actually use if they came back.
So, what removed cosmetic would you actually use if you had it?
So not just sit in your collection untouched for 5 years once the shiny new factor wears off.
You actually have to mog or ride it 
The mage tower weapons. Especially the druid and mm hunter ones.
There were a handful of appearances from the Mage Tower I wasnāt able to complete due to a medical issue I was dealing with at the time. I missed out on MW Monk, Unholy DK, and Aff lock in particular!
Most definitely the Cloudsong Glaive from WoD challenge mode.
Ghost of the Pridemother Feral Druid forms.
And the Black Proto Drake mount. My DH started working for Sabellian after the Legionās defeat and I try to use mostly Black Dragon themed stuff. I canāt stand the old Drake models though and I find the Protos have aged much, MUCH better.
Getting access to the original corrupted ashbringer mog would be neat. But itās also cool that itās wildly rare to see.
I just want to say this is a great topicā¦
But I cant contribute because I cant think of anything I would actually use. I already dont use 99% of the stuff I do have
MoP druid Cycle Armor
If it was possible to put them in the transmog collections, the original blood and night elf starting gear (before everything got stormwinded) would probably be my main cozy/casual transmog plates.
Also the mage tower rapier on my rogue (I didnāt have a rogue during legion)
Variety for bear druids is the only thing I can really think of that I would use often.
Brutosaur I only want for functionality and most of the removed mounts have in-game alternatives. Maybe the deathwalker mounts? I donāt think those have an obtainable version currently.
The Blood Troll bikini.
I donāt know if it will ever come back but Iām assuming it wonāt because assuming the worst is healthy lol
The original Corrupted Ashbringer from the original Naxxramas.
i already have all the removed cosmetics that i wanted in the game (MoP + WoD CM, Mage Tower). So, one of those, which i do use on a few characters. Nice.
Be cool to bring em back for other folks to earn as well, but i donāt see smol indie company making a wise bidness decision like that, even under a new parent company.
I wouldāve liked to have had Atiesh. Not sure how often Iād use it, but Iād definitely build a Guardian mog around it.
Still think they should have just put Naxx40 back in its entirety instead of the stupid āhere, you can have T3 for 3.5 million goldā monkeypaw. Itās not like it was removed for prestige reasons, they were just lazy and wanted to recycle the raid.
Cataclysmic gladiator paladin elite set recolor.
From MoP :
Lock, Dk, pally and druid sets
From WoD:
Season 1 PvP elite sets
Scourge Invasion blue Paladin plate set. Grand Crusader mount from ToGC.
^ Iād 
see myself using these if I had them.
Legion MT for Mistweaver essentially gives a staff that looks like you have a Chi-orb at the end. I would absolutely use it if I got it.
I think this would be it. I donāt really like the werebears, the shiny bears we can unlock atm look better. Not many other ālimitedā stuff appeals to me.