Medabots

Medabots is a video game franchise developed by Natsume and published by Imagineer, later adapted into a Japanese anime television series produced by Bee Train.

Plot
The series begins with a ten year old boy named Ikki Tenryō, who wants to become a champion of the World Robattle Tournament. However, Ikki is unable to afford a Medabot, and his parents refuse to buy him one. However, he manages to get enough money to buy an outdated model, and, with a bit of luck, he finds a medal in a river. Ikki quickly inserts it into the Medabot he purchased named Metabee. The only problem is that the medal he found gives Metabee a severe attitude problem (a problem rarely seen in a Medabot), which leads Ikki to think he is defective. However, this theory is proven wrong later in the series, as it is revealed that Metabee actually has a "rare" medal.