Resto Shamans, Duel Wield in Cata.

All one-handed spell power weapons are also main-hand only, which means an Elemental or Resto Shaman will be stuck using a weapon with physical DPS stats even if they spec into Enhancement's Dual-Wielding.

Still, at some point people were considering doing this anyway, since you can still use a weapon imbue on your physical off-hand (but not on a shield), especially since it gives you another chance to proc Earthliving Weapon.