I have a scar on the back of my right hand, I received it in the back of chemistry class in high school, but before we get to that, here is some back story. We were obsessed with wrestling at the time and as seen on television we would reenact fights in school despite the cautionary warnings to not try any of the stunts at home (which technically we didn't do). One of the things they would do in wrestling was to use small razor blades to cut themselves so that the choreographed moves would look like it had busted them open and covered with blood, an adrenaline pumped spectacle.
So one day at the back of chemistry class a friend of mine found a piece of broken glass on one of the back tables and jokingly threatened me to bust me open after we had been having our mini wrestling session on the back fields at lunch time. I looked at him and I said, "You wouldn't dare." With little hesitation he grazed the surface of my skin with the piece of broken glass, unknowingly that he was going deeper as he was cutting into me and he was also cutting into the vein. There was a moment of shock between the both of us, neither of us could believe he actually did it. We were both silent and we both looked at the wound which was surprisingly deep for a cut that was not painful at all. Within a few seconds blood started to come out of the wound and calmly I got up from my seat and walked towards the paper towel dispenser they had at the side of the labs, the teacher was continuing with teaching his class, none the wiser that my hand had a bloody cut. I kept pressure on my hand and still no pain, just a lot of blood and resumed with listening to the chemistry class. My friend was very apologetic and I just laughed it off.
This scar on the back of my right hand was one of the most visible scars on my body but the one that gave me no pain. The funny thing was, no one even noticed it until it started healing. Maybe there is something to be said about that.