Personally, I always prefer to use one-hand weapons and a shield on my Shaman, especially for Restoration. This is mainly due to the fact that there are more one-hand weapons suitable for Resto Shamans then there are staves or other two-hand weapons suitable for them, and very few classes need to roll on a shield with Spell Power. As for Elemental though, I guess I prefer one-hand weapons and a shield because it looks better on a Shaman... Though I'm always willing to switch to a DPS Staff if it gives a good damage boost.
Either way, there's just one stat I try to avoid like the plague: Spirit. Until Cataclysm, it practically has no use for Shamans. Anything else with Spell Power should be okay for Shamans to use though, wether it be for Elemental or Resto.
Oh, and Enhancement? Slow one-hand weapons and Hunter gear. That's all.