For mine, I would have to say Scourer of the Eternal Sands
by far. I had not been questing in Uldum very long (on my rogue) when the Tiny Camel Figurine popped up and I clicked it. Unbelievably, the thing teleported me to the Steam Pools first time and I found myself staring at Dormus the Camel Hoarder and wondering if I had the stuff to solo him. It took blowing all my cooldowns but I managed it and was rewarded with my most cherished title, "The Camel Hoarder". To this day, I have not seen more than a half dozen others on my server, so I wear it proudly, but only on the character that earned it.