The manual may be on the way out, but while we have it we're in a bit of a golden age of transmissions. We have efficient continuously-variable transmissions, we have eight- and (nearly) nine-speed automatics, double clutch shifters of all kinds, and we still have one or two gated manuals hanging around. But what's the weirdest gearbox ever made?
I'm not sure if it's the weirdest, but I have a certain fondness for preselector transmissions. Here's how you shift in one. There's a lever with all the gears lined up sequentially. All you do is move the lever into the slot you want and then depress the clutch and the car changes gear for you. It only changes when you depress the clutch, so it's something like a cross between a manual, an automatic, and a sequential gearbox. That, or maybe you can think of it as a very hands-on DSG with only one clutch.
You find preselectors in old race cars, like the ERA Tiff Needel tested on an old episode of Top Gear from 1991. Preselectors died out not long after WWII, probably from cost and complexity.
Surely you all can think of an even weirder kind of transmission, be it on a car, boat, motorcycle, train, or who knows what other vehicle.