I can see my pulse in my lower lip too. And I think my crackling neck came from two very serious riding accidents. If you've played any contact sport, or been in a car accident, or even had a chiropractic adjustment, that is most likely what caused the calcification that LindaRK speaks about (by the way, I had no idea that was what it was!)
I think one of my eyes might be slightly larger than the other. As LindaRK says, our bodies are not symetrical. A lot of ladies on here have complained that one breast is larger than the other, so the same is probably true for a guy's scrotum.