I'll always remember Asheron's Call for implementing the greatest Live event I've ever seen. I'm in the process of writing up an article about it, but in the meantime I'll link to a write-up I found:

http://www.ethblue.com/acpaper/page2.htm

That sums up the event in its entirety. It's worth a read to anyone curious to see how wondrous live events can be and should be accessible even to someone who never played the original game.

Later live events completely destroyed towns (I miss you, Arwic!) and introduced dramatic climate changes across the world. Turbine knows what they're doing when it comes to dramatic storytelling.