The one piece of gear you will never sell

I will probably never get rid of the Nakamichi 682ZX cassette deck, even though I plan to get into open reel deck adventure project.
I also really like the Nottingham Spacedeck but still might upgrade in a distant future, don't know.

There is not a single piece of commercially available gear I have that I could say that I would never sell. I do have a pair of custom built pair of Fried C3L with D2 woofer modules that my dad and I built from solid black walnut a couple of years ago. Although they are not cosmetically perfect, they sound pretty damn good and are never, ever going anywhere other than with me for as long as I am alive. Nothing will displace spending that time with him and creating them together. 

I do regret selling my custom C3L 20+ years ago...

I shall never part with my Jeff Rowland Criterion preamp.  EVER.

Thiel CS 2.4 SE loudspeakers.