Cars for me. Why is it that a car is designed in a way that if someone sneezes at a bad time then there will be an accident? I also think you should be able to see all the parts needed to operate the car (petals)
And tea pots that leak! It was supposed to do one thing ...
How about kettles? A container that whistles when your water boils. The never-ending list of errors: handles that are in the wrong place, whistles that don't whistle, underside heat distribution plates that come apart, lids that become wedged tight. After the centuries we've had to perfect kettles, you'd think a reliable design could have emerged by now.
Can’t wait till we can mass produce open sourced objects. E.g. 3D print on demand a kettle