I have a long list, but here's my top few:
https://www.youtube.com/watch?v=2z29Rk8814w [Big Blue Dress]
http://www.youtube.com/watch?v=xlULgi92zK8 [Beer Song]
http://www.youtube.com/watch?v=qQP53sse_-c [I'm Too Pally]
http://www.youtube.com/watch?v=QB49s4hlHVc [Amish Paradise]
https://www.youtube.com/watch?v=qX7ehxyYRQc [Welcome to the Deadmines]
http://www.youtube.com/watch?v=HpclJaSF7A0 [Craft of War - Blind]
https://www.youtube.com/watch?v=ltM5jHIJFw4 [I Play WoW]
https://www.youtube.com/watch?v=mIGSpnqn5Fs&list=PL6FC0AEA2BCB860B7 [Azerothian Super Villians]