Wii U. Played it for maybe 100 hours across its lifetime, which is significantly less than any other device I have.
Current gen, among my consoles, the Switch. Lived Mario Odyssey and Rabbids, like FE Warriors, but haven't bought anything else for it. Should easily surpass the Wii U in the next year though.
Of all my gaming devices in general, probably my Oculus Rift. VR doesn't lend itself to long sessions and before I got Lasik I had to wear contacts that my eyes rejected after an hour or two. Also, it gets HOT in that thing. Every minute in VR is fantastic, though, and despite my having used it for less hours than my Switch or Wii U, the time I have used it feels more valuable to me than either, so far. I'll cross that threshold sooner or later, though, and the Wii U will likely remain my worst gaming purchase ever.