In a game with thousands of quests, there must be one that was an absolute drag or another that made you laugh like a kid in a candy store. Take your pick.
As for me
Worst: City of Light
Reason: Oh great, wandering around Shattrath for what feels like ever.
Best: The Stoneplow series, ending with 'Savior of Stoneplow'
Reason: Such a dramatic quest line that had me use my karate techniques I learnt earlier in the zone on a giant bug in order to save the village.
Now it's your turn.