For those that haven't quite gotten there yet, I wanted to highlight a "Fun Quest" (as my category puts it). Really, it's more of a required quest line. If you have a toon at 80 and you missed these quests, you must go back and do it. Now.
I'm talking about the quest line for the Veteran of the Wrathgate achievement. It's probably best to simply go look it up on Wowhead on the link provided. It's about 20 quests for the Horde and 30 quests for the Alliance. I believe they're pretty much all in Dragonblight. Pretty easy quests. They're all soloable. Good xp as well.
Why should I drop everything to do this now, you ask? Am I that obsessed with achievements that I think you must do all of them? No, of course not. The reason for the urgency and prodding is that once you turn in Return to Angrathar (the alliance one linked, Horde one is here), you get to see this sweet in game movie.
I won't say anything about it to avoid spoilers, but I think it's a lot of fun how Blizzard really has thrown Arthas in our face ever since we entered Northrend, just like they said they would. It really feels like everyone has a chance to mess with him, very much unlike Illidan in the Burning Crusade.
What are you still doing here? Go quest, now!