Ok, this is a litte embarrassing but when I was 14 I was thinking about becoming a vet. My dad got it arranged so that I could watch a dog get spaded. I show up and there is this girl there that I know from school. Before the doc even begins to gut, as he's giving this injection I see blood backup into the syringe. Maybe my blood sugar was low that day or something because that was all it took and I hit the floor. Once I drank a coke though I went back in and finished watching the procedure.
Once at work, that was very embarrassing (I was working at a coffee place in the middle of a busy mall lol).
Luckily, I was grabbing paperwork.