Hand-down... its the electric Can Openener! I simply cannot operate one of them! Brand new or ancient, I can never get it to open a can without puncturing a million holes. I buy pop-top cans whenever possible because of this!
A close second would be the iron. It spits water droplettes when I don't want them and refuses to steam when I do. Then it scorches or isn't hot enough. When will they create self cleaning, self ironing clothes?
As for the dryer, isn't there a way to turn it off? Our buzzer doesn't buzz because we changed the setting... but I know what you mean - my mom's does that and she LIKES it.