Tauren Shaman for Elemental (Warstomp+Chain Lightning like Vashaman).

Orc Shaman for Enhancement (Stun resist in melee and using a hefty 2h Axe benefits from the +5 axes racial). Popping Bloodlust with other buffs can also result in huge numbers like Unbreakable or Xrave.

Trolls don't really have much and I regret making a Troll Shaman (I have been Elemental, Enhancement, Hybrid, Suicide spec). The main reason is that Female Trolls stand up straight and the Males actually look cool lol.

Don't forget Orc hunters and warlocks get extra pet damage. Maybe good for BM spec.