Avoid melee for PvP. It's so annoying to stay in a 5 y range, especially if you have some latency issues ... With exception maybe of Feral Druid, but Feral is hard to play as hell. Also avoid casters, who need to cast/channell a lot.
Go with BM Hunter or Elemental Shaman or Destruction Warlock. If you wanna try a melee, I would say Retribution Paladin. He's some kind of mixture between melee and range. Very very easy to play, but survivability is a bit of a problem.