Throwing Knives
Seeing someone who is a 'Master of their craft' can really open your eyes to new possibilities.
Every time I read any books about adding throwing knives to a self defense situation, they always left me thinking throwing knives were more of a curiosity rather than a practical tool. Similar to my idea of Nunchucks. They really would hurt if you got hit by them, but not very practical to actually get good with them.
Here in Canada it is generally illegal to carry knives, so there had better be a good reason to put in the time to learn to use them. Jason made an interesting observation that you can throw anything with a point, which opens the skillset dramatically. You will definitely get charged if you impale someone with a screwdriver, however that might be a small consideration when someone is attacking you with a knife or gun.
The one reason I can think of to put in the time learning to throw in knife is home protection. Craig Douglas of ShivWorks talks about using a weapon to 'gain space'. Usually a fighting technique or knife, which allows you to get to your gun and use it effectively.
Sticking a knife or screwdriver into a home invader might give you the time you need to get to a locked weapon in your house. It will certainly take some fight out of him.
You of course will not be carrying a knife around with you at home, but having one or two strategically hidden might be an option.
At about the 6 minute mark in the video above Jason Johnson was able to articulate a fully thought out concept of how and why to use a knife in a fight.
Being able to consistently and accurately throw a knife is not necessarily the only tool you want to have, but one tool to use in your toolbox.