Don't completely rule out shadow priests either.
I have a ton of fun playing as one.
I might not hit the DPS charts as high as a warlock or mage, but it isn't too bad and they're fun to play as.
I'm actually thinking about joining again and rolling another priest.
As for mage, warlock and huntard, I'd honestly go with a mage. They are really fun for PvP once you get the hang of it. Warlock and hunter both kinda bore me, both PvP and PvE wise. (only my opinion, and what's fun for me may not be for others, and vice versa.)