I have a great story from the LASER crowd. One can never be sure about such stories but I was told by someone...actually two people who claimed to be there.
One of my customers made high speed, high energy LASER drilling systems for the mass production of sheet templates for keyboards, printed circuit applications and such. This engineer, Tom, was once assigned to work the company's booth at a LASER technology fair. Being the yearly showcase for such technologies, the latest and greatest high energy IR LASER was set up for demonstrations. Of course, being IR, the beam is invisible, and for safety reasons the beam was kept below waste level. Near the end of the last day they had started to break things down when it was noted that the LASER was no longer aligned properly...and it was still turned on!
While reaching to shut the device off, Tom and his associates quickly followed the beam's path, scanned the surrounding area, and saw that some horribly large number of people had cuts or burns in their pant legs - all at exactly the same level. Just then they saw a burn form on another persons pants leg as he walked by. They quickly broke things down and left.