the most useless thing is the one personally you don't use.
I know that sounds obvious, but I cook stir fries about once a fortnight, so use a wok all the time, even my large frying pan isn't big enough for a mixed stir fry for 5. Dh makes nasi goreng and fried noodles in it too, and you need something deep.
But if you don't cook them or can fit it in your frying pan, why would you need a wok? (and why would anyone need an electric wok - that is a bizarre concept)
I use a pestle and mortar all the time, because I make a certain type of curry which needs the spices grinding.
I use a garlic press pretty much every day, I clean it with a brush, the dishwasher never works.
We were given a waffle maker, which we use because my kids love waffles, but I did need to get a recipe that worked from a friend who uses one.
But I never, ever make home made soup. Well, maybe once a year. And if I do, I make a large batch and stick it through the food processor, rather than use a stick blender. (and freeze the rest)
So a soup maker and a stick blender are completely useless to me, but my friend uses her soups maker at least once a week, for a small pan of soup for her and dh.
The moral of my story is, clear out your cupboards of things other people thought you would find useful!
But, just to be controversial, my most useless item is my slow cooker. I have tried, many time, and it is never as nice as just as food cooker in a real oven