Kaalis has a post on the forums about something that seems small, and yet is something I have never, ever, in all my years of playing this game, noticed before. Everyone (and I mean everyone) in Azeroth is right-handed. From the lowliest guard in Stormwind to the meanest boss in the Black Temple (probably not Illidan-- maybe Gorefiend), everyone who wields a weapon is right-handed. Even the Shivarra (those female demons with the six arms) wield their weapons in their top right hands. How incredibly strange.
I should correct that: apparently Blizzard noticed this before they did Zul'Aman, and so there is one NPC in all of Azeroth (actually one character, because all players are right handed, too) that is left handed: Nalorakk, the bear boss. And you have to assume that after this, we'll see other bosses and NPCs that might mix things up a bit.
But for players and old NPCs, Bornakk says not to hold your breath. Blizzard is working hard on new customization options for Wrath of the Lich King, but turning players southpaw isn't one of them.