It was the spine and the heart that did it for me. I found this to be the scan where you could look at it and say "Oh, it's human!" And Connor proved it by opening his legs and saying "Look at me! I'm a boy!!" Funnily enough he did it at the 25, 28, 32, 34 and 37 week scans too. Every time we had an ultrasound (and we had a lot) the sonographer would quickly pull the wand away from my stomach and exclaim "OH, do you want to know what the sex is?" We had to assure her we already knew and it was okay, he was a flasher :)