A chair having one or more dildos installed on it.

This strangely embarassing device features in pornography, usually of the BDSM variety, but I have never seen one in RL.
If one had a thing for classification (and I do), one could probably imagine:

  1. single dildo chair: fitted with a single dildo, or with a butt plug, it can be enjoyed by man, woman and everything in between.
  2. double dildo chair: comes with two dildos, and can be truly appreciated only by women.
Due to human anatomy, the two-dildo variety should probably have at least one dildo mounted on a pivoting base.
This, and the existence of inflatable butt plugs, allows one to imagine all sorts of interesting scenarios with the chair user being locked into the chair ... well chosen clothing could make the situation practically invisible to the outside observer. The possibilities are endless.

A more lightweight solution for the easily embarassed and the lovers of leather is the scrotal leash.

NEWSFLASH: Ikea categorically denies selling dildo chairs, and anyway it was distributed only in Sweden and it was a limited edition and mostly meant as a joke and we cannot sell you one.