Graduating high school; It shouldn't have been a huge moment but I had a horrible Junior year where I decided everything except for school was important. I had to take 2 summer classes, 3 classes through the mail and pass everything that year. It was a ton of work, and not having any free time to myself. It wasn't the best year of my life, but accomplishing it all made me feel good about myself. My parents were extremely happy for me (my dad never finished high school because he got my mom pregnant and had to start working full time), and I was glad I could do that for them.
Watching my little sister drive in the game winning run in her softball game, even though she didn't know the situation at all (she was 10). It was exciting, the last inning (due to the time limit) and they were undefeated until that point. Just seeing her hit the ball and run to 1st base, then afterwords the team on the bench running out to congratulate her.
Same question, with the same caveat for Shannon and Pekka (if they answer, share their worst).