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I'm an Altoholic. Currently have eight level 90 toons, two level 89, ten level 85 (my Horde set) and two monks (both factions) on the way.
My thing actually changes as I get bored of an aspect of the game. Right now leveling my Alliance set to 90 is the goal. After that I'll probably work on getting a horde toon to 90 for the achievement. Then, and probably while working on the horde toon, I'll finish all of the MoP quest lines.
I got Loremaster on my Horde Paladin before Cata dropped. I started collecting mounts and pets before they were account wide.
I enjoy the game much more with LFD.
For roles I enjoy both tanking and ranged DPS. My Paladins and Mages are my preferred toons, I don't have any class that I don't enjoy playing, and I have them all twice.