Haunted Memento was so cool and I have a story about mine.
I had 3 of them at one time. They weren’t always unique and I found 2 from the event mobs.
They also had a use-effect like a happy fun rock where you could throw them to other players so that’s how I ended up with 3.
I mailed one to an alt but then never checked the mailbox and took a break from WoW so I lost it forever.
When I came back my irl friend who actually got me into WoW was lamenting how he was never able to get one.
So I sent him my 2nd memento and the little butthead sold it on the AH the same day! I couldn’t believe it.
Anyway I only have one now and it’s on a server I don’t play on very often. The memento isn’t as cool as it used to be so I don’t miss it much.