What's the best and/or favorite piece of equipment you've owned? And do you still own it?

Apogee Calipers, yes I still own them.

Grado MCX yes.

Arc sp-9 mkI mkII mkIII yes.

Sota star sapphire yes.

One 

One of my favorite toys.  It’s keeps my babies safe n sound.   I will never sell it !

Favorites? Several pieces over the years.

AMPS: Music Reference RM9, Mac 225, cj MV50, Custom 6BG6 Conn amp, B&K EX442 Sonata & ST140

PREAMPS: Music Reference RM5 mkII, Museatex AVC-1, Aragon 24K, Superphon Rev Basic DM, Technics SU-9070, Hageman Hapi2

INTEGRATEDS: ASL MGsi15DT, Audio Space mini Galaxy, GemTune GS-01, Onix OA-21s & OA20/2, Tandberg 3012, JVC A-X55 Super A, Meridian 551, Creek 4330

TT: Thorens TD125 mkII w/Rega RB303, Rega Planar 3, Linn Basik/Akito, Kenwood KD5077, B&O RX

CD PLAYERS: Proceed PCD2, Rotel RCD855, Cambridge Audio Azur 840C, Audio Alchemy DDS Pro

TUNERS: Meridian 504, Sansui TU717, Pioneer TX9800, PS Audio ST1, Perreaux TU-1, NAD 4300, NEC T710, Dyna FM3, Creek CAS 3140, Sumo Charlie

RECEIVERS: HK 330C, Tandberg 3030

CASSETTE DECKS: Nakamichi DR2 & BX125, Kyocera D811, HK TD392

SPEAKERS:  ProAc Studio 1’s, Paisley Research AE500’s, Focal Chorus 807V, Tannoy 635/D90, Omega Grande 8’s & Super 3XRS, Monitor Audio R700 MD, Linn Helix LS150, RFT B150, Chateau Research 1.5’s, Rauna Tyr II

Sorry that I can’t narrow it down to just one or two things.  I’ve enjoyed this 40 year journey way too much :)

IMF Mark 4 Monitors, Improved. Great speaker in all categories if you have enough juice. I have a Threshold 4000 so that covered it.

ATC SCM50ASLT active loudspeakers in rosewood. Will never sell these. I've rotated through many speakers over the decades.