Arduino in the same vein. There’s a great “30 Days Lost in Space” tutorial set, but even to play around with by yourself for cheap, you can get an off brand (the hardware is open source!) Arduino Mega for 20 bucks. All sorts of cool programming and electronics fun.
Not a lot of products have to do that. The one people bandy about is McDonalds adding “Caution: Coffee Is Hot” to their stuff, but the actual coffee spill lawsuit was over coffee hot enough to cause 3rd degree burns. Few things need cautions against their intended use.
Q-Tips / cotton swabs are an almost uniquely bad tool. It’s incredibly easy to rupture your ear drums. There’s no actual health benefit to swabbing your ears – it just feels good your ears get itchy. A safer tool could be made, but it’d be more expensive, more involved to use, and there’s probably several but I can’t be bothered to find out, and neither can you. They make a product that they know is inherently dangerous to use and has no specific benefit. So it has a warning against doing it. Same as cigarette packs have a warning that they cause cancer, even though everyone buying them knows that and smokes them anyway.