A year or two ago, I went to the local hospital for blood tests. I have small veins that aren't close to the skin, so nurses often have difficulty drawing my blood. I can usually tell them where the best spot to try is, but on this particular occasion, the nurse was really having a hard time.
I got her to try my left arm first, as always, but she missed the vein and wanted to try my right arm. I prefer not to use it because of nerve damage that makes having the thing around my arm feel rather uncomfortable. She tried my right arm, but missed again, so she went back to try my left arm again. This time she missed the vein, but left the needle in my arm and wiggled it around, trying to hit the vein. Eventually it slipped out of my arm, and she jabbed the end of her finger with it. This meant that they had to test me for AIDS and various other diseases, despite that she'd gotten more blood out of herself than out of me. A second nurse tried then, and succeeded on her first try.