Enlightenment (and horde equivelent)
http://www.wowhead.com/?item=47960
-From heroic twins is an excellent weapon for a shaman. Sure it's not best in slot, but its at least in the top 4-5 weapon combinations for an elemental shaman, especially good for those who don't have much luck getting a better shield than pulsing spellshield. It all depends on if its an upgrade or not. It's not for scrub shamans as some people say. Sure the Heroic shield from Faction Champs and the Mace from Heroic Anub25 are best in slot, but not everyone is going to be able to get that. Enlightenment and cold convergeance are fine choices.