This sort of question comes around every once in a while; "what's your must-buy under $100", "what goods would you recommend for people just moving out on their own", and so on. I love reading these because, despite my simply vast experience[^1], I sometimes pick up new tricks.
This question is about second-level stuff; maybe not "must haves" that you'd recommend as a first purchase, but the stuff that makes life easier, that you might acquire after you've gotten settled. Things that you may have only discovered that you'd buy again if the house burned down.
For example, my wife bought a couple of these microwave tools years ago, and at the time I thought they were going to be gimmicky stuff we never used. Turns out, we use them all the time; whoever came up with the idea was brilliant.
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I like them because, unlike a hot mitt, if they get food on them you just wash them. They're way easier to use than mitts, and can be used more securely one-handed. I wouldn't trust them on stuff from the oven because of their size, but for plates and bowls from a microwave, they're surprisingly handy. It took me a dozen times using them before I realized the ring in the back actually works to clamp them to the bowl and turn them into a handle, rather than just using them as grabbers.
The thing I used today which prompted my post, and something I'd encourage people to buy if they don't have one, is a battery-powered rotary tool. My current one is a Dremel 8250, but many companies make them. They're handy and make short work of a lot of odd jobs, and IME if you have one you constantly find places to use them.
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A kit like this one runs about $150, and I think it's worth the price. I think it's worth getting an accessories kit, but the bits that came with the kit are the ones I use most often and can take you a long way.
So, what are your tools, devices, or products that you've discovered which may not be a common, basic first-level "must have" household item, but which you'd not want to do without? Things which might be a little off-the-beaten-path but indispensable? Stuff you may have stumbled upon which turned out to be surprisingly useful?
[^1]: a.k.a. advanced age
[^2]: Image grabbed randomly from a web search
[^3]: Image from product page