If you want to see 9-year old boys crying, I guess you could let them watch Old Yeller for the first time or throw their DS down a well. Equally effective is to go to a middle school wresting match.
My 9-year old got the first two beatings of his career yesterday. Losing one-on-one in front of a big crowd is very humbling in a good way. Getting dumped on the back of your head then pinned after waiting 2 1/2 hours for you second match is pretty much unbearable. It's pretty stressful for the parents as well.