I was thinking about artifacts recently. Thought it might be kinda cool to have ultra-rare, unique per server super-powerful items (think of the axe from VON1, the staff from Rainbow, or the items from the dead Gauntlet players in Shroud 1) that can drop anywhere, and only stay with a given player for a limited time, then sneak out of his inventory and appear somewhere else at random. They would bind on equip and could be traded normally until bound, but doing so would not reset the timer.