I did WALSTIB on three toons and had two more almost ready to get it when I found out that the VPD would no longer give Master Riding for free. Ah, pity. The mage and DK probably won't ever do that (though I could afford Master Riding on all my toons if I really wanted).
And I did the Wintersaber quest before they changed it to match the raptor quest. The only way I found to make that bearable was to do it at the same time as I ground out Timbermaw rep and to time my runs (I got it to 15 minutes/cycle for an hour or two).
Anzu and Ashes. They are my favorite mounts in the game, even still, so I farmed and farmed and farmed all of my characters. 4 Anzu, 2 Ashes. I still feel bitter about it.
Here's another discussion on wasted items, along the same lines as the OP: anyone have any items they regret vendoring before transmog? I have too many to name, but I mostly regret the Undead Slaying set I got during the end of BC.
Oh god.
I had a full set on my shaman and rogue that I know of, and I think I had a set on my priest. I DISTINCTLY recall vendoring it on the shaman and the rogue to save room, though.
At least the parts I had on my hunter (3/4, missing the chest) survived for transmog.
The other thing I wish I hadn't vendored was my paladin's Halberd of Smiting. At least there'll be models of it in 5.2.
Oh and I also paid 25k for the Drake of the northwind drake that took aprox 101 runs from a hunter friend, I barely even use it in addition I did 505 runs normal stonecore literally yes I tallied that BS to get that drake as well I had to duel box a friends hunter because every single friend of my hunter was like NO MOREEEEEEEEEEEEEEEEEEEEEEEE so one let me borrow his account. I also randomly gave a sandstone drake to someone for free yes.
<.< too much stories
Every time I see someone in it I want to punch them in the face. I wish they'd add a vendor for them, or even that the old vendor was still there (shoulders/gloves are better than nothing). I have Necrotic Runes in my bank...God knows why I kept those but not the gear >.<
Bought 496 bracers from AH for 30k (trash BoE) which got replaced by 502 heroic BiS one next reset. Nice way to waste gold. Now it's irrelevant, I have near half a million left and prefer having good RNG over bad one but here's more wasteful example:
In my nooby times in march (2 or 3 months into WoW) i bought 2x pyrium spellward (365 ilevel agility sword) cos i loved the look of swords on my back. Didn't knew that HoT heroics with 378 ilevel gear existed. That was when I barely had 10k gold on me and spent almost all of it on those swords.