Thinking about technology on my run today. The bicycle came to mind as the technology (non-medical) with the greatest upside and least downside. The bicycle is very efficient for local transportation, but far from the most efficient means to do any particular harm.

I was once run all the way down by a drunk cyclist, and got up with minor scuffs.

I'm trying to think of other technologies that are both useful and very hard to use directly for evil.