You used to be able to mail the shield to a horde char and it would turn into the gul'dan staff and if you'd put an enchant on that you'd mail it back to ally and the shield would have the enchant still on it. It's gfd now tho.
Horde players received a Replica staff of Gul'dan. Alliance players received a Replica Lions heart shield.
Both items are cosmetic, with no real stats on them.
However, when you'd mail your staff to an alliance character, it would turn into a shield.
This means you could enchant the staff (while it is a staff) with a weapon enchantment, then mail it to alliance.