from UC's pages comes the Harmaki, a piece of asian armour which should be in every character's gear list.
a quick overview: cost of 3 gold, and weight of one pound. not a burden even at first level. this armour is without any penalty for the wearer, not even arcane spell failure, but it still gives you +1 ac for your troubles. it can be worn beneath normal clothing without being obvious to observers.
so why should everyone have one?
Casters: +1 ac with no penalty or real need for proficiency. at low levels its quite worthwhile as a 'keep you alive' device, while at higher levels it can be enchanted for bolstered AC without bracers of armour.
skill monkeys: this stuff is casual wear, allowing you to pass without suspicion in most disguises while still providing some protection.
heavy armour wearers: again, casual wear. it's fast to don if you're ambushed (if you're not sleeping in it) and if you want to go around town without drawing suspicion but without leaving yourself too vulnerable.
admitted, it's not the most protective armour in the world, but it's cheap enough for all but the most skint of characters to carry one as backup. the only reason outside of flavor that i can see for someone not to have one as backup (along with your silver dagger and darkwood buckler) is if the game doesn't allow oriental armour.
so, what have i missed?