My oven does something that really annoys me.
When you press the Bake button, it starts blinking, and 350 is displayed. Then you use the up and down arrows to set the temperature in 5-degree increments. (That really should have been 25-degree increments, but that's more forgivable.) Anyway, once you finish setting the temperature, you press Bake again, it beeps, and you're done.
Except you're not. When you press Bake again, 350 is displayed. What? It was blinking! It turns out that there's a separate Start button that's not even connected to the Bake button. Pressing Bake just sets the temperature to 350. This would be annoying enough as it is... except for Timer, they get it right. To set a timer, you press Timer, set the number of minutes (in 1- or 10-minute increments), then you press Timer again. To turn it off, you press Timer once more. This is exactly how I would expect it to work. It's more sensible, and only requires that one button and the up/down buttons. But for some reason Bake and Timer work completely differently. And, I use the timer far more often than I bake things, so after 13 months of living here, I still end up resetting the temperature to 350 half of the time, which is really annoying if you just pressed the up arrow twenty times to get to 450.