I love Logitech mice, so I actually dug their shameless mouse timeline. Even more awesome, though, are these amazing prototypes that never left their lab, like the three-scroll wheel monstrosity and hockey puck above.
They get wonderfully cheeky about them too, saying that the hockey-puck mouse "looked cool but turned out to be less than comfortable." (WINK WINK NUDGE NUDGE.) Here are a few of the more ridiculous ones, but be sure to check out the whole run. It's hard to believe some these even made it off the page, much less into a polished, physical form in some cases. Of course, none of them will ever top my beloved, retired MX500.