Wearing little to no armour, but armed with a crossbow these peasants can give far superior soldiers a nasty surprise.
It is said, that in Granada, every peasant owns a crossbow. Certainly they are popular with the Moors of Southern Spain, being both easy to use, and effective against well armoured Christian foes. Although they can't afford armour, they can give their betters a nasty surprise. A wise commander won't rely on them too far in combat though.