I got sharpshot (sharpshooted?) on my presentation today. Although kryptonite wasn't in the lesson plan, I fielded a question from an overzealous classmate asking about Superman's weaknesses. This was followed up by a question from the class smart-ass of "What does Blue Kryptonite do?"
Upon reflection, I hazarded the guess that it kills vegetation. His retort was that it provided a benefit.
Some fact-checking shows that we were both wrong. Blue Kryptonite is the result of using the imperfect duplicator ray on Green Kryptonite. It is only harmful to Bizzaro and other Bizzaro Supermen, in the same ways that Green K is harmful to normal Kryptonians.
I'm not even going to get into, "Would you consider compassion to be one of Superman's weaknesses?"