For me, it’s an electric toothbrush. It doesn’t matter if you go with Sonicare or Oral-B, once you start using an electric toothbrush, regular toothbrushes don’t ever feel like they clean your teeth properly. The smooth plaque-free top layer of your teeth that you can feel after using an electric toothbrush can’t be replicated with a regular toothbrush.
There’s actually a pretty cool community sort of tangentially related to this! !buyitforlife@slrpnk.net
Anyway, my pick is definitely just a GOOD mp3 player. Whether that be an open hardware one you can crack open and repair, a proprietary one that can at least be Rockboxed, or bare minimum a proprietary one with a good iFixit rating.