its somewhat faded and shortened now, but i have an Inch long white scar running diagonally on my upper right arm.
I used to work as a Glazier to help pay my way through Uni, and one time i was (With 3 other guys) working on a shop front in the small and pikey town of Stevenage.
It was a saturday, and sometime on friday night some drunk had chucked a bin through the main window of a shop, it was quite an old window so wasn’t safety glass - just very thick (8mm) so had shattered into shards.
Anyway we had cordonned off the shop window and the doors next to it (people could still get in by using the set of doors further up).
I climb a step ladder and start carefully removing the shards at the top - always start at the top and work your way down - when one of the guys asks me to give him a hand with something. As i reach the bottom of the steps and pick them up to move them, some complete and utter muppet of a member of the public walks under the cordon opens the door, goes through and lets it slam behind him with a BANG…
which shakes the window…
which dislodges a 6 inch shard of glass…
which falls about four feet…
which passes through the leather safety gauntlet i was wearing…
and embeds itself in my arm with a spray of blood.
Luckily one of the guys on site was the company’s First Aider, and he stopped anyone pulling it out, slapped pressure on the wound, and rushed me to the hospital not even waiting for the ambulance. it was bleeding quite badly and i was somewhat lightheaded by the time we arrived.
I was bloody lucky that he was there because (they told me later) i’d actually clipped an artery (which he’d recognised) and if it had been pulled out then i’d have lost a lot of blood, and if they’d done that AND waited for an ambulance…
…well, not worth thinking about really.
Needless to say that guy rarely has to buy his own drinks when i’m around. 
Unfortunately the doctor who sewed me up was damn good at his job, so all i’ve got left as evidence of what was a pretty major wound is a measily inch long scar.
Bastard. 
On another occasion, i was working on a building site when a JCB swung round and managed to put its bucket through the window above where i was working inside, luckily i had that whole “sixth sense” thing happen and was already twisting away as it started raining glass. Whilst most of it missed me i did get several nasty slashes down my right hand side just above the waist, and have several very prominent scars there.
I’ve got a couple of other minor glass related injury scars (including one on the back of my left hand that was caused pretty much the same way as the first one i described here) but i’m one of those people who heals pretty cleanly, so you can’t really see them unless you know where to look.
i actually have a much larger red scar on my upper left arm. Unfortunately the story behind it is less-than-cool:
i was viciously attacked by a boiling hot chicken pie as i pulled it out of the oven.
I tend not to tell people how i got that one.