I'd like to see off hand items (though not necessarily true off hand just equippable in that slot) that provide unique effects/debuffs. Arrowhead for bow users that has a chance to apply a debuff of some sort. Like some on said earlier, an oil or sharpening stones for melee and runestones for casters.

I would prefer they just be items instead of consumables. They could also come with instead of a debuff but a special effect like increasing buff durations or stat heavy to allow a smidge more customization for the jobs (i.e a +dex oil so tanks can raise parry if they choose).