"Ribbon awarded for being an exceptionally hard worker."
This ribbon is awarded to a Pokemon when they have maximum Effort Values.
Ruby/Sapphire/Emerald: Slateport City - Given by a woman who stands in the marketplace.
Diamond/Pearl/Platinum: Sunyshore City - Given by a woman who stands to the left in the Sunyshore Market.
HeartGold/SoulSilver: Blackthorn City - Given by the woman on the right in the house to the right of the Pokecenter.