Vibrators. Hitachi is also known for their powerful, corded vibrators (it's not a dirty word): the Magic Wand.
Calling these 'marital aids' in 2023 seems a little outdated. Vibrators are devices used for sexual stimulation, which obviously makes them extremely useful for solo masturbation as well, in addition to being a sex toy someone can use on another person.
All magic wands are amazing (not just the hitachi ones, but try to find a decent brand like hitachi, bedgeek). Trust me guys, they're so good in many spots; treat yourself!
Vibrators have a lot of interesting heavy industrial uses. At massive scale, things like paint mixers are massive vibrators. I had a college friend whose job title on LinkedIn for many years was "Vibrator Engineer" due to specialization in that industrial field. I don't think any of the vibrators they worked on were "personal sized" and I doubt any of the companies on their resume had any plans to sell sex toys, but that was an industrial/mechanical engineering specialization important enough to those companies to be reflected even in job titles.
Relatedly, my favorite Japanese product line enigma remains Yamaha realizing that all the finely specialized industrial equipment for building organs and pianos could probably be multi-tasked to making motorcycles.
