The Daily Grind: What's your favorite MMOG expansion?

With the upcoming World of Warcraft expansion, Wrath of the Lich King, Lord of the Rings Online's upcoming Mines of Moria and the recent announcement that Rise of Kunark is the #1 highest selling EverQuest II expansion as yet, we've been thinking about expansions. Some people insist that all expansions are is catering to the endgame raiders, in creating more levels to run through before serving up new raid instances. Other expansions do bring in things for lower-end players, like Burning Crusade and Rise of Kunark introduced new races to play, and new areas for them to play in. Today we'd like to ask you what your favorite MMOG expansion has been to date and why? Which games desperately need an expansion to bring something new to the game?
This article was originally published on Massively.