As soon as you obtain the Falcon in this brave new World of Ruin and fly around and beat up helpless ostriches, you notice some weird new pieces of equipment that start at the top of your equipment list but are never equipped with Optimum. Also, why is it that they don't appear to do anything? Well, they're meant for imps! Imps!
Imps do not benefit from the Defense and Attack of most equipment, including Fists. One point is added to both Defense and Battle Power instead when you equip something that's not meant for an Imp.
However, there are four pieces of Imp equipment (that's an entire set) that are meant for Imps. They include the Impartisan (non-elemental Lance every character but Umaro can equip), the Tortoise Shield, the Saucer helmet, and the Reed Cloak, all of which sport incredible Defense and Magic Defense while absorbing Water-elemental attacks and teaching the Imp spell at a x1 rate.
They don't fully work unless you have the Imp status, though; Attack Power and Defense of these items are reduced to 1 when they are equipped on a character that is not an Imp. Magic Defense, Evasion and Magic Evasion do still work, as does the elemental properties and the spell teaching.
Win an Reed Cloak from a Sprinter, Steal a Saucer from a Tumbleweed, Steal a Tortoise Shield from a Basilisk and Steal an Impartisan from a Greater Mantis and you've got your Imp warrior right there. Turn a character into an Imp, equip away, and you have a character that excels in defensive properties yet lacks a little on the offense. This can be remedied by giving this Imp warrior the Dragoon Boots and a Dragon Horn; the ultimate Dragoon (remember, the Impartisan has an Attack Power of 254, which is far superior to the strongest 'normal' Lance). All this guy lacks is versatility. It's up to you if the lack of special skill and Magic skillset (not to mention a possibly cool set of sprites) outweighs the defensive and often offensive advantages of this Imp Dragoon.
Personally, I feel that Cyan and Sabin make great Imp Dragoons as they lack the Magic Power for a truly effective offensive Magic skillset and they lose very little with their special skill since the average Jump result isn't too much weaker than Flurry/Phantom Rush. I should also add that Setzer could also be pimped this way while still keeping the Fixed Dice, since the damage output of the Fixed Dice ignores the Imp status of the wielder.
And, if nothing else, whatever. You've got an Imp in your party, and that's awesome.