This is going to sound insane but, trick weapons like Monster Hunter's Charge Blade, Switch Axe, and Gunlance. Some jobs can equip specific trick weapons related to their role, i.e. WAR can equip both Charge Blade and Switch Axe while also being able to equip all 3 role weapons, PLD can only equip charge blade along with their standard Sword and Shield and can equip axes, and DRK can only equip the Switch Axe, greatswords, and axes. MCH can use use gunblades/lances and maybe turn their turrent into a second gun. BRD and NIN could probably use Bows that also double as twin swords, DRGs obviously get gunlances. Also RDM already have their rapier that doubles as a staff.