Superstar guild Nihilum (H-Magtheridon-EU) has apparently gotten Lady Vashj, the final boss of Serpentshrine Cavern and Illidan fangirl extaordinaire, down to 3%. This means the world first kill is probably not far off. In the grand tradition of end bosses for large raids, this follows after a hotfix nerf to Vashj a week or so ago; Ragnaros, Nefarian, C'thun, and Kel'Thuzad (I think; not quite positive on KT) were all nerfed before they were first defeated.
Being as how nobody's ever killed her before, we don't really know much of what she might drop (other than probably T5 tokens like the rest of SSC and the Eye). But we do know one item: the Fang of Vashj, a one-handed (i.e. not restricted to main or off-hand) dagger with the following stats: "92.8 DPS, 133-201 damage, 1.8 attack speed, increases attack power by 50 and increases dagger skill by 14." We know this item exists because it's listed in the official Bradygames strategy guide, although besides its name we have no actual confirmation that it will drop from Vashj. If those stats are accurate, it would be the highest DPS one-handed weapon in the game, aside from the epic weaponsmithing weapons (Blazefury, Dragonstrike, and Wicked Edge of the Plains).