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.
To be fair, the early ones were pretty crappy compared to what they have now.
At the start, you really couldn’t use it for real work. The convenience came at a huge cost.
These days all but the most extreme tasks can be done with cordless.