Speed bar is a pretty general term that I suppose could conjure up different images if you don't actually know what a speed bar is. If I say speeder drive handle instead then some may catch on to what I'm referring. Still in the dark? A speed bar is a socket drive tool designed for high speed, low torque operations. Its shaped like a crank and requires two hands to operate. They work fine but in these days of battery powered tools I doubt you'll see many techs actually using one.
I recently rediscovered the speed bar while installing my automower this spring. Those long course plastic screws hold the charging pad down to the ground and it turns out a speed bar is the perfect tool for the job. A power tool can easily "strip" the screw in the soil and prevent the screw from holding. The speed bar is as sensitive as your touch and you'd have to purposely overtighten to run into problems. A power tool needs a battery and of course is expensive to leave dedicated to an install kit that doesn't get used every day. Speed bars are like unwanted step children and can be found most anywhere neglected tools gather, and they don't need a battery.
So there you go. I'm happy to get a speed bar out of my tool box where it was just taking up space and keep it in my mobile automower kit where it will actually be used. Take a look in your tool box at those unused tools. You just might find a new purpose for some of them.