Although I'm sure there have been several more minor incidents where I have been treated unfairly, these are the three most major ones I have experienced:
In elementary school, I was in band class and tried to impress my classmates by playing the Pocahontas song "Colors of the Wind", which I had taught myself by ear. Everyone in the class started booing me and the teacher told me to stop playing. Then my best friend at the time sat down and started playing the piano and everyone liked it (she had taken lessons). Someone said I had a lot to learn from her. I smiled and agreed, but on the inside I felt like crying. I don't play the piano much anymore.
When I was in junior high, I confessed to my best friend (the same one who had upstaged me at piano playing) that I had fallen in love with her. It was true - I had had many crushes before her, both male and female, but she was the first one I truly loved. She said she didn't feel the same, and I told her that we didn't have to be friends anymore if she didn't want to. A couple of days later, she and a group of her other friends (who were notorious around school for being bullies) handed me a note that said, among other nasty things, that I was "revolting lesbian slime" and that "[I was] going to Hell and [she wasn't] going to get dragged down with me." Although the group of girls could have easily been punished for homophobia, the school did nothing about it even when I went to the counselor and told her what had happened.
When I was in my teens, I was suffering from a bad case of anxiety, depression and OCD (all of which I later went on medication for). Naturally my parents were very worried about me and spent time taking me to therapists and the psychiatrist. My older sister (who is ten years my senior) was very jealous of the attention I was getting, and when our younger brother approached her and asked what was wrong with me, my sister said I was exaggerating all of my problems so that I could get mom and dad to pay attention to me. She began driving my brother to and from school, and during these car rides, they would talk about how much they hated me. I had no idea this was going on at the time, though my relationships with the two of them were volatile. I found out about it several years later when my brother confessed what had happened out of guilt. When I confronted our sister about it, she said that she "didn't know how bad [my] problems really were" and that it was everyone else's fault for not informing her.