Wireless Trackball M570
Used by 6 peoplelogitech.com ↗

“I got the Logitech M570 trackball years ago when I had issues with my hands and wrists and like it a lot, especially the trackball is great (I love a speedy mouse).”
Lena Reinhard Interview, Director of Engineering, CircleCI · via Uses This 

“I use a Logitech M570 wireless trackball instead of a mouse.”
Ada Palmer Interview, Science fiction & fantasy novelist, history professor, musician · via Uses This 
“The Model 01 has some basic mousing functionality, but whenever I'm doing something at all mouse-intensive, I'll switch over to the Logitech Wireless Trackball.”
Jesse Vincent Interview, Developer, CTO of Keyboardio · via Uses This