I've had plenty of mice, far too many actually. I've had an uncountable number of wireless Logitech mice, and other random non important mice, but here is a list of the ones that I feel are worth mentioning.
Current: CST LtracX (best trackball available, but could be better still.)
#1 small mouse: A4tech x750bf (really wish i could still find these in the USA, my last one finally died)
#1 large mouse: Microsoft Intellimouse Explorer 3.0 (most comfortable, smooth tracking, loose scrollwheel(which is better))
Other Mice:
microsoft Intellimouse optical 1.1 (best weight, good texture, smooth tracking, side buttons are wrong though)
microsoft optical 1.0 (best texture, would be my #1 if it had side button's and the tracking that the 3.0 has)
a4tech x750(smooth texture ruins it)
Worst mouse: Razor copperhead (jittery, bad drivers, soft rubber wears quickly, mushy feeling soft scrollwheel)
Best mouse that I don't like: Logitech 518 (hurts my pinky).
Most uncomfortable mouse: Contour mouse (large) (really it's just painful if you have to keep lifting it)
EDIT:
Ok I forgot, I don't know if this one counts, but I think the absolute worst "mouse"/input device that I've owned award has to go to the OCZ Neural Impulse Actuator.