While the single-die tool system provides an easy way to handle most items and their uses, sometimes you want a little more depth for a unique or unusual item, making them something of a character themselves.
The most obvious application (and inspiration) for this is in dealing with animals, such as horses or dogs. In addition to their die as tools, the animal may possess aspects of their own. A great clydesdale horse may have Giant Draught Horse, or your horse could have Unusually Clever, Stubborn as a Mule, Trained Warhorse, Built for Speed or Mean as Hell. Canine aspects are endless as well. Hunting Dog, Lazy, Hound of War, Loyal, Half-Wild, and Ferocious Appearance are all good examples.
This could also be used to represent items of with unusual qualities, such as magical items or other tools of unusual characteristics. Particularly significant items may have more than one aspect. One can quickly imagine a ring with the aspects Concealment d12, Longevity d8, Sought after by the Enemy d12, and Will of its Own d8.
Players may invoke aspects of animals or tools at their disposal by paying a point of ardor as though they were invoking one of their own, but must also endure the aspects of their items, when applicable. Finally, the GM can compel the aspects of objects under player control. The danger is that these compels cannot be 'bought off' in the way that player compels are, though they still earn ardor for the player in question.
At the GMs discretion, certain objects may grant bonuses on their own. The enchanted sword Elvenbane might have the aspect Hatred of Elves d8 that automatically fires whenever the weapon is being wielded against an elf. Such weapons would be very powerful tools, by CF standards, and should be used sparingly, if at all.
It should be up to the GM and his players whether dice earned in this way should count towards the vigor limit of the player invoking the aspect. If not, then tool aspects become very powerful factors. If so, then balance is struck with other aspects of the system, but the vigor cap may wind up preventing the tool aspects into coming into play in many situations.
The above gives some basic suggestions, but the idea can establish a precedent that can be used in countless ways, from animals to weapons and armor to ships and vehicles - any time you want to elevate a tool from an item to a character of its own.