I am surprised that no one has mentioned a mechanical wrist watch so far.
What an amazing piece of technology a mechanical watch is!
It actually changed the world, respectively the way we look at it. A mechanical watch of high precision and extreme reliability was the only way to determine your position on the globe back in the 18th century, solving one of the biggest problems in understanding the globe and its geography.
I gives me immense pleasure to wear a really nice mechanical time piece, a birthday gift. It's got the most user friendly interface that is, in that it gives you precisely the kind of information you need at a glance.
I can't imagine to replace it with anything of today's visions of wearable computing. Apart from its questionable usefulness in currently discussed models, I know that no one will wear anything like that for longer than the lifetime of the particular product, which you can estimate at 2-3 years, maybe.
I know I will still wear this particular watch in 20-30 years, so this is definitely a technology that I will never give up.
Just like my Kenwood TS930 ham radio transceiver from 1983. It does what it is supposed to do and no other product on the market gives me same features and quality in my particular requirements. So this will be my last transceiver and I won't ever give it up. Got a spare one to make sure I will always be able to maintain this beautiful piece of technology.
Another thing: I bet that in a 100 years from now there will still be completely mechanical grand pianos out there. Despite all modern means of imitating sound, creating effects, simulating and powering concert halls with nifty digital sound processing, there will still be the need of an unamplified instrument that people will enjoy listening to. A piano from good makers such as Steinway, BÃsendorfer, Yamaha, Fazioli etc. is a mechanical marvel. Mostly hand crafted, it achieves a level of perfection, both in mechanical engineering and from an aesthetic point of view, that is a pleasure to play and to listen to.
Oh, and the cassette tape. Still got hundreds of them and a variety of playback devices. Used to tape concerts with one of the professional walkmen from Sony and still listen to these. Won't give up cassettes either.
 Full break-in capabilities at high speed morse without any clipping, analogue receiver throughout, i.e. no digital signal processing for maximum signal discernability in pile-ups, fully documented technology with standard components, more or less open source.