Iron Horde Scraps

Iron Horde Scraps drop from any Iron Horde mobs in outdoor Draenor and inside Warlords of Draenor instances while characters have a War Mill or the Dwarven Bunker built at their garrison.

As currency
Scraps are used as currency for transmogrification items, sold by Kristen Stoneforge in the Dwarven Bunker at Lunarfall, and by Grun'lek in the War Mill at Frostwall.

As a quest objective
Patch 6.1 adds a daily quest that exchanges 25 scraps for an Armor Enhancement Token or a Weapon Enhancement Token:
 * Scrap Meltdown