I call this one The Prototyping Mouse. I don't think this will be the final mouse (more below), but a fun project in the meantime. It is just a SketchUp now. I will update the parts list later, when I can get part sources I can afford. It combines a trackball with a breadboard, to allow any type of switch to be placed anywhere. Ideal for perfect mouse button placement, or cloned buttons to allow for quick hand position movement for people who develop pain in one position (e.g. trackball with forefinger, buttons on left/right, switch to trackball with thumb and extra left/right buttons to the right side.)

My mind thinks of endless examples to plug into it: different combinations of tactile switches, switches with labeled key caps, variable resistor, capacitive touch controller, a 555 timer circuit for rapid fire, motion sensor, LED's, TV remote circuit, jumpers to other projects, or anything that can be programed with a Teensy.

It has two arrays of 32 x 32 for 2048 possible connections. It is made up of more than 64 1x32 0.1” female headers.

Bottom is a skeleton view without jumpers or Teensy circuit.

I split and left a gap down the middle so I could tilt the left and right sides for comfort, maybe spring loaded. I can't see this as the final project because of some ergonomic flaws. I am still brain storming about something contoured to my hand, but this looks too cool and will give me the experience I will need when I develop something better.