I was always a fan of the Amiga 1000 mouse. Later 500 and 2000 mice LOOKED the same, but the mice from 1000's have bigger balls. It really does make a difference. For the longest time I kept replacement pushbutton switches, and I replaced them as often as needed to keep the mouse feeling fresh.
All my classic Amigas are gone now, but I recently found a box of mouse repair parts, including enough parts to put an A1000 mouse together. I gave some thought to transplanting a wireless laser into it, but the loss of the mousewheel would be a deal-breaker for me.