hmm PvP? I would spec one Holy, and then 4x Frost... oh no wait, thats DKs and a Pally.

Priests? I would spec them.. well i have no clue, they don't work (i have tried) 5x shadow and 5x holy is pretty beast in large scale PvP, though, and you can really help your team out a LOT with any of those specs, and even disc, with a random target shield macro, i guess. but holy for the circle of healing and Prayer is probably superior. with a LOT of gear, shadow would be pretty ballin, but getting it will be.. hard.

fun though, and this is from someone who plays Arcane mages in PvP.. which is even dumber than priests! but FUN as hell (I do have 10 though.. which makes it.. 2x MORE FUN!)