Prot pally / Ele shammy..

..or Prot pally / AoE mage. I used to dual-box split-screen with a prot pally on the left and a frost/arcane mage on the right, and it was awesome having the pally tank a dozen mobs while I rained blizzard / frost nova / cone of cold / arcane explosion on the group. Food/water/CC/ports.. fun stuff.