I got one from myself and one from a friend.
I took martial arts, and one day in class, I got pretty badly injured. I hyper extended the tendon in my left foot. At first it seemed like nothing happened, but when I couldn't stand on it without searing pain, I had to go to the doctor. The doctors told me that if I put weight on it, my tendon would snap and require surgery. So, I had to walk on crutches for one or two weeks.
I got permission to leave classes 5 minutes early, so I could avoid the mob in the halls. But this didn't help when I first got to school. I had to walk in the crowded hall. I remember one day, while walking past the library some random guy that I didn't even know knocked a crutch out from under me, which of course made me react by putting my foot down to catch myself. I was so angry, but I didn't even know who did it, and even if I did, what could I do on crutches? What kind of jerk kicks a person's crutches out from under them?
There are more, but I think this was one of the worse of my high school career.
Now, for my friend. Personally, I can't believe anyone would give him trouble, because he's a good 6 feet and a few inches tall. But people gave him trouble for years because he was a bit of a loner (I didn't know him at this time), and would say that he was going to bring a gun to school and shoot people. One day, this one punk actually hit him. Long story short, my friend blacked out and the next thing he knew he was being pulled off the kid and there was a hole in the wall the size of the kid's head (it was a trailer). He really doesn't remember what happened, but he does know he never had trouble from any of those people ever again.