Blessed Orb

"Randomises the numeric values of the implicit properties of an item. Right click this item then left click another item to apply it."

This item only modifies the implicit mods of an item. A list of items and implicit mods are visible on the POE item data site. For example, bows (http://www.pathofexile.com/item-data/weapon) do not have any implicit mod and a blessed orb cannot be used on them (as it will fail).