All the ancient quests I did for the old Loremaster on my pally back in the day before Cataclysm. Having originally leveled a toon mostly questing in TBC, trying to figure out what quests I had left in mid-Wrath was a bit of a hassle. A very rewarding hassle I would do again any day (week, month...), 'cept of course I can't anymore. Oh well.
I think I enjoyed Loremaster more (the first time) than even the AQ sceptre chain I also finished around those times. AQ chain required too many other people to truly make it only my effort, whereas all the Loremaster research I did for myself by myself. The only thing I still majorly dislike about Cataclysm are all the lovely quest chains that went away.
Thanks for getting me back on Nostalgia Express, I guess.