I've had this digimon idea since I was 12 years old. It's based on a old old mouse with the track ball.  ReyCovert helped me a lot with this, so i take no responsibility for the lines here.

Trackmon:
Ultimate/Perfect Level Digimon
This digimon always holds onto there little ball. The ball acts as a mode of fast transportation, unfortunately the ball attract every foreign object. They frequently clean there ball in order to keep it's movement. Despite the ball being a separate part of them, they refuse to do anything with out it. Taking away there ball and they will refuse to move, cry, and throw a tantrum of the ages.

There attacks include:
Plug and Play - Terackmon plugs there tail into another digimon, taking control of there movements and attacks.
Double Click - Trackmon makes an piercing clicking sound that paralyzes there enemies.
Scroll - Trackmon's ball increases in speed, and can zoom away.