Are you my brother? He & his friends did this in our back yard, and it was my (teenage at the time?) older brother who ended up with a dart in the middle of his back.
They took turns on the tree swing, while the others threw the darts. Mike got a tetanus shot that day!
Remember Silly String? An aerosol can that shot out this plastic goo jet that solidified before it hit the ground
Not real dangerous in itself, but if you combined it with an open flame (let’s say – maybe a birthday cake candle) you had yourself a nice flamethrower. And the burning goo would stick to what (or who) it hit.
Oddly enough, my sister is named Kathy.
But she’s my older sister.
And my dartboard impression was never shared with my family members. 
I made an air gun using an old bicycle pump and the tube from a pen. It would shoot nails with tape wrapped around them with quite surprising force and accuracy - it would easily put a nail through drywall, as I discovered.
Never actually used it on a person, though.
I was a kid when safety came in, so we had to make our own danger.
Take a regular black Bic mechanical pencil apart. Break off the stylus end and insert the graphite-holding tube in that end. Loop a few strong rubber bands over the pocket clip and over the eraser on the end off the tube. Now put, say, a BB in the body of the pencil, draw back - and you’ve got a BB gun capable of chipping teeth from across a classroom.
I keep imagining a parody of Rudolph the Red-Nosed Reindeer, in which among other things instead of visiting the Island of Misfit Toys they visit the Island of Unsafe Toys, where all the unsafe toys have been banished. The head toy would lament: “Every year, the stupid little bastards find a new way to kill themselves with even the most innocuous toy!”. Then at the end Santa would distribute all the unsafe toys to boys and girls who would procede to maim and kill themselves with them.
Was I the only one who had a heavy paper cap powered bomb? Looked like like a small metal ball with dart flights but it was made out of lead or pot metal and weighed a ton. This sort of anvil thing in the head popped a single cap. Or the whole roll, if you threw it hard enough, like, say, at a car. Or through a window? Oops.
I had one of those, but don’t remember playing with it very much. Probably lack of ammo.
Sweet jesus, I’d love that on a cross-stitch sampler.
I remember dissecting a formaldehyde soaked frog in a poorly ventilated garage bathroom. Probably not something I’d let my hypothetical kid do now though; I got a doozy of a nauseated headache and my friend Nicole actually barfed and had to go home.
My brother was very accident prone so I never got to play with anything more dangerous than the science kit stuff. I had to improvise with the aforementioned Aquanet flame throwers and flinging myself off of things and down goat trails while playing “Movie Stuntman,” my favorite made up game for a long time.
I was a kid hit right between the eyes with a lawn dart (and obviously survived)–I believe that the brand was called Jarts. Anyway, while at a friend’s birthday party outside, I stood on the sidelines while a little girl threw one wobbling high and to the side. The sun was in my eyes. Next thing I knew, I was on the ground with blood all over my face. The mother-in-charge consoled the weeping little girl, and I pretty much was ignored.
A friend who seemed well-off had a great toy: a metal frame would pull down a square of plastic over a metal form that had reached a super-hot temperature from the heater below. You could create car bodies, soldiers, planes, and so on. Very dangerous.
My godmother worked for a chemical company. I could obtain large quantities of zinc powder and sulfur to experiment with rocketry. One day, I accidentally lit a vat of mixture in my room–blew holes through much of the room, and burned myself badly.
Long before that, I carefully cut open the blisters in caps, and collected the black powder, which I then used to create miniature charges for a small cannon that would strike out at some toy soldiers. Now that I reflect on it, I certainly burned up a lot of stuff.
Found directions for making a sling (not slingshot). Managed to smash a window a block away. Ended my sling career.
That was a Vacuform IIRC and I still remember some of the burns that thing gave me.
Off-topic, but #13 is the one that caught my eye…
Shrinky dinks are still around!
We had the Creepy Crawlers set with the thingmaker and the flower one. Since I was the girl I was supposed to use the flower one and my brother got very possessive of the others. We also had the Incredible Edibles.
We had cap guns but at some point my mother said no more toy guns. She also wouldn’t let me have a Click-Clack because she saw the potential danger before the makers of them did.
It’s kind of funny the toys my mother tried to protect us from but when we were outside we did all sorts of dangerous things that didn’t even involve toys. I especially loved climbing trees (tomboy) and I’d often climb the tree next to the house then climb over on the roof and run around on the roof. When we visited my grandparents farm we’d climb on top of their shed and jump down into a hay pile. I can’t believe that we never broke any limbs.
You should send that idea to Robot Chicken; it would be perfect for that show.
I haven’t seen mention of frisbees yet. Today’s state-of-the-art golf disc is 170+ grams of dense plastic with an edge. People hurl those things with all their might. A friend of mine got hit by an errant drive on the bridge of his nose–not a pretty sight.
Boomerangs! I just remembered coming within a hair’s breadth from smashing out one of my grandmother’s house windows with one.
The Bic pen launcher just reminded me: take a bobby pin, bend one of the “arms” around in a kind of loop so that it can be cocked against the other arm. Touch to a person, and it snaps out quite painfully.
Others have mentioned chemistry sets, which are great toys. They used to come with poisonous chemicals–my bottles of Cobalt Chloride were marked as a serious hazard. I kept worrying that I had accidentally poisoned myself.
A trick an adult showed me: take Saran wrap (or anything similar), twist quickly into a vague rope with a knot at the top (which you hold). Hold over a saucer on the floor. Light the end and as liquid fire falls off, you’ll hear a satisfying zipping sound. Terribly dangerous (and goodness knows what we inhaled).
For some reason too many people thought you played Jarts like horseshoes. Why any moron would stand opposite another moron throwing a weighted steel pin at you is beyond me. You each played from the same side!! Click Clacks were indeed made of glass because I could never figure why they would chip but not shatter - never could get the hang of those things. Finally, did you try this? Taping an M80 or Cherry Bomb or Hammerhead or WHATEVER size portion of dynamite to a golf ball and hitting it? I grew up with a neighbor who THREW those damn things short fuses and all. Also, Wrist Rocket shooting an M80, and I mean Wrist Rockets from the 70’s that actually launched something. Oh yeah we also rigged an M80 into a model rocket which had an oversized engine AND we would lend M80s to the local black fisherman who fished for Carp in the Gunpowder. One in the water brought manna from the mud! I could go on - those were the days my friend
Does anybody have a link to the hilarious old SNL skit with the Mob guy selling broken glass as toys? I remember Bill Murry (in a phoney italian accent) saying something like//“da kids can play all day wid diss stuff”!