Plue

Plue aka Nikora, "The Canis Minor" is a Silver Key Celestial Spirit that has no obvious combat abilities and is stated to usually be kept as a pet for low-powered Mages, but is as powerful as any other character in the game Fairy Tail Gekitotsu! Kardia Daiseidou. Lucy Heartfilia seems to use hers, named Plue, as a pet and a comical character. Nikora keys are shown to have been sold for as little as 20,000 Jewel.