Winix air filters, since we were self-quarantining. We bought one, and it was so good on removing dust and smells and smoke that we ended up with three. They clearly improved our stay-at-home experience, as our house is one of those 'air-tight' energy saving constructs.
Also we purchased two battery backups, one for a fridge to keep the frozen food in decent shape for a few hours, and one backup to support internet connectivity. [Inspired by pandemic supply chain glitches. we ended up with extra frozen food items.] After seeing their usefulness in power outages this summer, we might still add an even better backup battery, that can run microwaves.