Love loads of these things mentioned - lumea - life changing! Ninja foodi - used everyday and still so many more functions to discover.
Mine are
Kitchenaid stand mixer - had it 8 years now and never used it once. Baked a lot of cakes back then and always reached for the £5 Argos hand mixer
Kitchenaid blender - use a £5 hand held blender for soups, apart from Oreo milkshakes one summer it’s never really been used, it’s so heavy and unwieldy.
George Foreman grill - never used. Sandwich toaster - got bored of toasties quickly.
Steam mop - well reviewed on Which but doesn’t clean well at all.
Jackets - all saints one which looks lovely but is a bit heavy to wear. Rick Owens bargain at £1500 which I wore for one autumn and then got fed up at the long arms which go up to my fingers.
Love my robot hoover, even though he gets stuck every night under the sofa.
Baby bike seat which got used for one outing. Bikes for me and DH which got used for one outing.
Years of expensive supplements and ovulation sticks and pregnancy tests- the body does what the body wants, and none of it helped me get pregnant.
Handheld Garment steamer which still sounds like a good idea, I am thinking of giving it a dedicated space which might encourage/remind me to use it more 
Jimmy Choo heels - cant see myself wearing heels again, prefer flats, wore them once or twice
Can’t live without my Lakeland heated airer, dries one whole load reliably and folds up to rest behind the door. I guess it’s horses for courses!