I like the Clemente one alot. I think that's a real good one. Also Bo Jackson. Heck, he coulda been great in TWO sports.
I'm gonna throw out some guys that we are watching now and are having constant injury problems and could have been great if not for them (and may still be great a some point in the future)
and sadly, I think Ben Sheets, given his last couple years. He's been dominate when he COULD pitch, but too much time on the DL.
I can't imagine what Jr. Griffey's career woulda been like if he'd managed to stay healthy. He was amazing, and still is a pretty darn good player. What would his stats be like if he had all that playing time in his prime back though?
His injuries always made me kinda sad and I'm happy to see him still being productive.