I haven't even got any great mental scars to talk about. I had an idyllic childhood and grew up happily naive and well-protected.
Even the car crash that broke my back didn't leave any scars - not one! I had a bad concussion and a crushed vertebra, but didn't even bleed from any scratches. (Bruises, yes, but those faded.)
I suppose the most notable scars I have are the least noticeable of any of them: they pepper the back of my eyeballs. So, I will use this entry as a public service announcement. If you are highly myopic (near-sighted), have a family history of diabetes or blindness, or see floaters or flashers, get your eyes checked by a professional. And I mean, thoroughly checked, not just a prescription for your glasses. Get your eyes dilated and let them shine that headache-causing light at the back of your eye while you follow the dot around. It is a medical procedure, if you are a high-risk case, and your insurance should cover it even if you don't have vision coverage. Especially do this if you're seeing more flashers or floaters than usual, or if things seem vaguely dimmer than they used to.
It saved my sight.
My freshman year in high school, my retinas started detaching: http://www.webmd.com/eye-health/tc/retinal-detachment-topic-overview
(I'm actually horribly disappointed in that link. Where's the gross picture of an eyeball lying on someone's cheek with a floppy, loose retina, eh?)
It wasn't too bad when it was first looked at, but by the time my non-serious, minor, out-patient surgery rolled around, they had degenerated so far that it ended up being a massive, multi-hour (my memory says 8, my brain says my memory is a weenie and probably doesn't remember correctly...) surgery on BOTH eyes as opposed to the scheduled single surgery, I was literally days from being completely blind and the damage was enormous. I had to stay in the hospital for a week, and wore a patch over the most afflicted eye for several more weeks. My ophthalmologist makes it sound like the back of my eye is more scar than not, now - basically hot-glued into shape with scarring.
My right eye is held together by a plastic band to keep strain from tearing the retina more, and both eyes have intensive laser and freezing scarring that seals up all the tears. The plastic belt is called a schleral buckle, and there are some illustration pop-ups here: http://www.webmd.com/eye-health/scleral-buckling-surgery-for-retinal-detachment#hw187647
I have the full wrap-around kind. If you put your finger firmly right at the edge of my eye and I look all the way to the left, you can feel it sliding around under my skin. I'd call it a party trick, but there are more people I DON'T want touching my eye than the other way around.
I'd say 'show me your scars, I'll show you mine,' but there are a lot of things I don't want to see, and you can't see mine without dilating drops, so we'll just skip that and I'm going to go to bed so I can get up for my meetings tomorrow.