I once had a ford rental car with turn signals that made me actively avoid using them. They felt OK, but the clicking of the relay was fake, a recorded sound. All seemed good until you cancelled the indicator. The computer sometimes kept playing the fake clicking sound. It kept clicking for a full click cycle every time you cancelled the indicator mid-click. It was only a fraction of a second, a full second at most, but I always thought that I had failed to cancel the indicator. It was both the smallest and most annoying problem I've ever had with a car.

2nd most annoying: Driving a US-made care in a country using the metric system. The cruise control is incapable of being adjusted a single kph, instead the minimum change is some number of mph. So you are stuck doing either 99 or 101, but never exactly 100 kph. The source of the problem is confirmed where the cruise control can be set to 80 kph, which is almost exactly 50mph. I venture that no BMW has ever had this problem.