The Ploopy Adept Trackball is an input device that looks a bit like a Kenginston Expert trackball, but it has more buttons, a smaller trackball, a 3D-printed case, and a completely open source design.

Trackballs are an acquired taste. Some look on them as oddities, but here's a confession: I've been using a trackball for well over a decade and find the arrangement comfortable and easy to work with.