Soldering irons. No matter how much solder I use, the joint does not last long. I've been trying to make cold joints, but those don't work long at all. I've gone through dozens of soldering irons, none of which work right.
Inexpensive electric power washers. Don't even get me started.
Factory bagel slicer = crap
Every time we get those packaged half sliced bagels you can never get them apart neatly. They always tear into chunks and won't separate. Why slice them at all? We always have to use a knife. No bakeries close by so we buy those. But I have never understood why they can't make a better slicer. If it is to protect freshness that's BS.
String trimmers, now that the rabid, know-nothing environmentlists sucking at the federal trough are designing the engines.