I think I desrve an honorable mention
For the use and creation of one of the worlds most questionable devices.
About 20 years ago, the commercial fishing laws were very lax, and I was making a lot of money spearfishing. I had this cool monster gun made out of 2 spear guns bolted together. On the left side was the small gun, the largest spear gun sold, with a 5/16 " spear. And on the right side was the same gun, with the stock extended. It shot home made spears that were 1/2 inch thick and 5 ’ long. These I welded to a short piece of 5/16 stock, so it could be fired from the standard hand grip. It needed 2 bands, but could shoot the heavy spear 50’ underwater. Now I could shoot a 40 lb grouper (worth 100$) with the heavy spear, and still have a second shot to move in close and finish him off. So far so good, I was killing big fish and making real money. I was sure I was a genius. The gun was so heavy it could not be held out straight to fire, so I fitted a open bottomed can halfway up the barrels. This I could fill with air from my regulator, to buoy up the guns, then tilt it to spill air out, after I shot the 5 lb spear, so it wouldn’t try to float away. 
I had always had my share of disagreements with sharks. However, the unique sound of the large groupers thrashing and dying seemed to draw in larger and more disagreeable sharks, then had been the case with the smaller fish I had been shooting previously. So after the second time I had my fish stolen, I was getting kinda angry. It is often dangerous to be clever when you’re angry, but I was to mad to care.
I knew there was a thing called a bang stick. This was a long metal pole spear, with a chamber for a 12 gauge shotgun shell at the end. If you jabbed the shark with it, the shell would go off.
Trouble was, it was large and unwieldy, especially since I was already swimming with the worlds largest spear gun. So my clever idea was to cut most of the pole off, and drill a 5/16 hole in remaining stub, so it would fit on the end of the small spear. Now, if a shark showed up to take my fish, I could pull this thing out of my pocket and put it on the spear tip, pull the safety pin, and be disagreeable myself. I was amazed no one had thought of this. Some things you can’t buy, so I made this myself.
Talk about excitement ! The first time I tried it I said “Make my day” to a 10 foot bull shark as he closed in on my fish. I let her rip from 5 feet away, hitting the shark on the nose. It was real surprised. I was too, cause the shell didn’t go off. I had been told that all you had to do was paint the primer with nail polish and it would be fine. But water had ruined it. The shark wheeled around, came back and took my fish. With a spear in it. I was really really mad. Now I had lost a 100$ fish, and a spear.
So now we get to the dangerous part. It was obvious that more experimentation was required. I got a fresh shell, put silicon gasket seal on it, and went out to the boat the next day.
I decided to test it in shallow water next to the dock. I wanted to test how far it could shoot before it had slowed to much to go off. So in about 5 feet of water I stretched out horizontally to fire it 10 feet into a wooden dock piling. Instead of crouching on the bottom. That’s what saved my life.
There was a loud base thud (a shotgun is surprising quiet underwater). A ball of gas. But no spear ! 
It had completely vanished ! Eventually I found it, about 30 feet behind where I was when I fired it. The shell had propelled the spear back at me, passing at high speed just under my body. Had I shot it at a slightly different angle it would have skewered me like pig.
Oh well, now I know why they don’t sell those things. I was never to use the shark shooter again. 
