Ow.
Most of my best scars are stupider, but just to spread some warnings:
-If you smoke, always have an ashtray present. You never know when that lit end's coming loose.
-When the screws on your chair start falling out, don't kneel across the seat (to retrieve an ashtray -- see, smoking's dangerous, kids!). It'd also be a good idea not to buy chairs made out of a sheet of carpeted cardboard screwed to four jagged metal tines in the first place. (This is the best one at the moment, only took a long scrape but it looks like I got shivved.)
-Don't slam doors with glass panes in them.
-Don't drop plates on your toes. (Ooh, medical laser!)
-Don't run down the hall barefoot with a freshly sharpened pencil. (The podiatrist still doesn't know how I got it into my ankle -- the eraser end hit the baseboard, you'd have to have been there to understand.)
-Don't ride a bike with your eyes closed. :insane:
-Don't test the soldering iron for hotness by holding it near your upper lip. Even if it makes sense at the time.
-Similarly, don't drop the hot iron on your wrist. (If you must, let it only be a 15W, like I did.)
-Don't bite off the side of your tongue for no apparent reason. (Another childhood one, I don't think I was chewing gum at the time... Strangely, this one occurred in the presence of the great-uncle who told me the story of his fingertip growing back...)
-Don't be Floid! :-D
Strangely, I have no health insurance right now... and have never managed to acquire a permanent injury from bungling with computers... maybe they like me. :lol: