3D printers, hands down. These used to be ridiculously expensive, janky pieces of technology that fought against you every step of the way and gave you shit results. Nowadays you can just buy one, put the parts together, plug it in and start printing straight away. They've come a really really long way in the last ten years.
As for how they've improved my life, I don't even know where to start lol I've made countless woodworking jigs which would have cost me a ton of money. I've made several replacement parts and adapters for things that I use at home. I've made a ton of fidget toys to keep my ADHD ass entertained during video calls.
3D printers are cool and you should make sure that you have one if there's ever a healthcare insurance shareholder conference in your city.