I use a trackball in my right hand. I use a trackball as it's more ergonomic, and I've had wrist pain in the past from using a mouse. I use my right hand because the oppressive burden of living in a rightie dominated world has made me somewhat ambidextrous. I switch to a mouse in my left-hand for the occasional times I'm gaming.

My last two trackballs have been imports from Japan. Apparently somebody claims a patent on the trackball, and sued Logitech, who have since ceased production of them.