About the only one, my husband had to have was an electric tabletop grill - "Lean, mean, grilling machine".
He used it once, filled the kitchen with smoke, burnt the sausages he was grilling on it, and it's not been used from that day to this. It sits on the kitchen worktop, unloved and unwanted.
An electric fondue pot, a slow cooker, and a stand mixer. But my pet peeve is drawers full of redundant kitchen tools (cooking spoons, spatulas, knife sets, etc.). A couple of each are useful. Five or six of each is a PITA.