Heard this one from one of my military instructors. He was instructing Saudi Arabian Airforce students on the Pilatus PC-9. Apparently the students didn't like strapping themselves in tightly and when the instructor was demonstrating something involving negative g the student thought he was going to be thrown against the cockpit canopy. As a result he grabbed the nearest thing at hand to steady himself which happened to be the seat pan handle for the ejection seat. This of course caused the seat to fire leaving a very surprised instructor in the back seat on his own with a rather large hole in the canopy. Luckily the instructor was able to safely land the aircraft where it was found that this particular student also didn't like to tie his shoelaces to tightly as he'd left his flying boots behind in the cockpit.