Commodore 1351 Mouse
Most of the C64 users (including myself) used the joystick to navigate our way through the vast multitude of programs. Nevertheless, for the more office oriented programs, a mouse would come in handy.
The Commodore 1351 was a great little device, with good response to movement and good firm grip.
It even had the ability, if booted with the right button held down, to emulate a joystick.