The Imperial system. It SUCKS. What I hate is how I WANT to learn Metric, but since I was taught Imperial all my life, I'll never know it. Main reason was my Republican father who said "the dumb Brit system is not needed in America".
Sometimes I do wish I'd been raised to think in metric terms, since even with all the crazy 'murrican units, I find myself using some of the smaller units. After all, we don't really have much that can be comparable to millimeters and milliliters and milligrams. o3o
Then again, there are tiny units like grains and caliber and mils, but who even uses them? Well, except gunsmiths, but I doubt many people can think in such units readily.
Also feel free to share other things which either your own country or some other country does retardedly different from the majority of the world.