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

My favorite piece(s)  are  (and I still own them) the Martin Logan Ethos lousdpeakers and Soudsmith Paua cartridge.  As far as speakers go, electrostats are my favorite and will replace them with another set of electrostats.  I'm currently eyeing MUR Audio SP1's.  These two pieces make my rig sound great.  
I'd say my old favorite was when I got the NAD 2020 integrated amplifier about 45 years ago. I wish I still had it but changed to an Adcom 5400 amp about ten years later. Current favorite piece is Watkins Generation 4 speakers (prototypes labeled "custom design" with Bill Watkins name underneath). Before those speakers, I had Watkins WE-2, a smaller version of the massive early 80's WE-1. I was also quite fond of my old Grace F-9E mm cartridge which was used with the NAD years ago.
I will never change or part with my speakers, but I do change components infrequently.

Now, the next thing I will never part with is my Vintage McIntosh mx110z Tube Tuner/Preamp.

If trouble presents itself, It will be overhauled by Audio Classics pronto.
Dead, I would buy another without ever considering an alternate.
Things you would replace without considering alternates?

You make me realize I have several things I won’t change unless they die. Keep in mind, I’m 72, so over many years you get to keepers.

As I said, I will never change or part with my speakers (custom enclosure/vintage drivers from 1958). I have a full set of spare drivers downstairs, and just checked yesterday, the vintage cloth surround re-cone kits are still available for the 15" woofers.

I also said I will never part with my Vintage McIntosh mx110z Tube Tuner/Preamp. I just wrote this AM, to Audio Classics asking them what they might charge to ’upgrade/overhaul’ them (just to know). If trouble presents itself, I’ll drive up there, 5 hours away, drop it off, visit my friend who lives near there. Dead, I would buy another without ever considering an alternate.

My TT, just added a 3rd tonearm to Vintage JVC Plinth CL-P2, I will never change that plinth. Spinner, TT81, never change it unless it dies, then direct replacements are available. 3 Arms, no desire to change, but if any arm dies, I would search, consider alternates.

SUT, new to me Vintage Fidelity Research FRT-4, if it died I would get another one just like it. It's 3 inputs match my 3 arms, and 4 optional loads give flexibility for future MC cartridges.

Reel to Reel, Teac X2000R, I have 2 active and 1 spare, their last ’Prosumer’ model, never consider another, I know all about their innards.

Office TT, vintage Vertical on top of BC. Only vertical will fit. Mitsubishi LT-5V is so cool looking, and a high quality linear tracking, I’d get another if it died. I’ve got some spare parts downstairs, but mice ate the electronics, so only physical replacement parts are good. They made similar taller units ’Interplay’ with vertical Tt and cassette and fm and aux input. If this died, just for fun I might go for one of them.

I frequently mention Chase RLC-1 Remote Line Controller for remote volume and remote balance. I will never live without two, 1 main, 1 office, and I have a 3rd on the shelf.

Oh yeah, my 8 Track Player. POC, but I designed the offices of Columbia House, and it was a gift.
Favorite? Probably would have to be the Linaeum Model 10 speakers bought at Corner Audio in Portland back in the 90's. Linaeum was a small company making speakers with an interesting driver that was basically a normal dynamic driver that instead of the voice coil driving the usual cone they removed the cone and replaced it with a plastic ribbon.  

It looked like what they did was glue a straight brace right across the center of the voice coil and attach two ribbons to it. These curved out kind of like a horn, only they kept curving around all the way back 180 degrees, and they were very flexible. The idea being the wave form travels or ripples along the ribbon for very low moving mass. The Model 10 used two of these back to back, a dipole in other words.

Whatever the story the sound was the sexiest most luxurious 3D sound stage presentation, probably that I have ever heard. I mean, an audiophile friend who was no fan of my system nevertheless said you weren't listening to a soundstage, "you're swimming in it."

They had problems. Voice coil heat could melt the ribbon if played too loud for too long. But the real problem was they had a real prominent bass hump. Sins of commission really are worse than sins of omission. Yet its my favorite? Maybe because another saying is also true: Absence makes the heart grow fonder. 

Best? That's a close call. Synergistic Research Atmosphere Level III Euphoria interconnect. Hard to believe an interconnect can be so good. But I would probably have to give the nod to my Tekton Moab speakers. Transformative, they are.
Teac X-7R reel to reel.  I no longer have it....if it would’ve been a car, it would’ve had 500,000 miles on it when it gave up the ghost.  Absolutely loved that machine, but it definitely belonged to another era, IMO.  I wouldn’t seek out another one now...
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My Macs, C20, MC240, I've had a few. This pair though, they were made for each other Though I'm REALLY liking  the Cary V12r, I've been tinkin' with over the last year. This is out of 45-50 different power amps, and preamps

The speaker, I currently own. VMPS RMx Elixir. and a few that I've made
and kept , and or still working on..So there is 10-12 pairs, 3 pairs unfinished, CLOSE though...COLUMNS.... Everything else GOES.

I keep a cool 1/2 dozen to a dozen  Russco, QRKs, or Spartas, for TT project every now and then.. Garrards are too expensive. I like Thorens too 124...a little more reasonable.. FUN stuff. easy to work on, and sound good.

I lost a Fairchild 750 all dolled up.. I was pretty sore about that one.. I would have never sold it... Was stolen... I still cant figure how they loaded it up. 250 lbs..

Anything with copper....




My dac Starting Point systems is irreplaceable soundwise and moneywise....I hope to own it till my death...

Oh yes MC, Joe Weber at Corner Audio. Spent lots of money there, Joe got me into high end audio.
It is not my best component, but it’s my favorite component, largely out of nostalgia: My Thorens TD166 MKII turntable. I still own it and use it. I bought it (with my parents’ help) in 1977 or 1978, at Audio Consultants in Evanston, Illinois, while I was still in High School. After 15-20 years in storage, in 2018 I brought it back into the Audio Consultants shop, had it serviced and overhauled, and a new cartridge (an Ortofon 2M Bronze Verso) installed, and put it into service in my system. It was great to see the owner Simon, who sold me the turntable so many years ago, in the shop. While getting the turntable sorted, I also bought several new components from Audio Consultants to get a great 2-channel system up and running. Simon has since retired, and Audio Consultants is now closed, to my sadness and dismay (but happiness for Simon). This may not be a top of the line turntable, but it still sounds great. And, I was loyal to that shop for more than 40 years, having bought many things there over the years.
The Maplenoll Ariadne Signature TT i still own modded with extra arm and 100lb platter and custom motor. Regretfully it makes my large digital music collection sound uninspiring and has therefore decimated my choices  about 80%.
As much as I love listening to audio, when it comes to physical possessions I'm 'way more emotionally attached to my musical instruments and to my record collection. That being said, I guess I got to say that my favorite component is my PrimaLuna Integrated.  Not only does it give me lovely, immersive sound, when something gets noisy it's fun to turn it upside down, take off the bottom and squirt Deoxit on the offending knob.  The 'Luna is so wonderfully straightforward and un-tweaky.  Then again, I've suddenly developed an unmistakable yen to audition a Grandinote Shinai.
Oh yes MC, Joe Weber at Corner Audio. Spent lots of money there, Joe got me into high end audio.

Those were the days! Joe was one of the very best. He was great like that. Let you alone to listen. As good as his stuff was, you couldn't help but get hooked. 

In those days I would go to Portland a couple times a year. Must have visited every high end store along the five from Seattle to Portland. Wish I could remember the tube amp Joe had, and the rest of the system, it was superb. Absolutely superb. And people talk about the room, it was a cube! A freaking cube! Horrible dimensions! Yet he got wonderful sound. So there!
To get some idea how good his system was, my wife got dragged along (it was her family in Beaverton) and that first time we heard the Model 10 speakers on the drive home she asked me if we could buy them. They were $2500, and I had just spent $1700 on speakers not a year before. They were that good.

My Decware Rachel integrated. At low levels, that thing was sweet as hell. The midrange was to die for. I wish I had kept it instead of selling to upgrade. 
Original Rogers LS3/5a 15 ohm , purchased new in 1975.  Sold in mid 90s along with all my other equipment to raise cash to start a business.  Ted to see them go, but the business was the best decision I ever did.  I could buy them back, many times over, but, kind of like the high school sweetheart- reality probably not as good as the memories.
Lafayette KT-550 tube power amp for one.  It was built in the 50s and still kicks the ass of most any amps I have ever heard even in stock form.  Other than that, the large Ohm Walsh I had in college playing dark side of the moon.  After that it is all the products I build.

Happy Listening.
My Sonus Faber Electa Amator speakers. They are the original ones, bought new in the 1990's, with the marble/walnut stands. If I can pick two, it would be my Stax headphones (currently 009s).
Lot's to choose from but probably my Nakamichi Dragon. I was a cassette deck-aholic! Next would be my 70lb Thorens TD125 Black Forest Edition with SME Series 3 tonearm and Shure cartridge. Currently I love my KEF R series speakers and SVS SB 3000! I'm now an HT junkie...
Oops right in addition to the Ohm Walsh since 1982 there is my Linn Axis since 1986.
My Apogee Duetta Signatures. Purchased in 1991. Still the centerpiece of my system.
For me it’s my Shindo Monbrison preamp.  I had discounted the importance of the preamp in my system before I got that one about 5 years ago, even though I had gone through some good ones.  
The Shindo just made everything sound better, full and rich and layered and textured and natural, with lots of detail, no matter what other components or music I throw at it (and I’ve changed a lot of components during the last 5 years). I doubt I’ll ever part with it, unless somehow I can afford to go further up the Shindo preamp chain, which would be quite expensive.  
And no, I’m not a believer that it has to be all Shindo or no Shindo.  It’s my only Shindo component (outside of some cabling), and I think at least at the preamp level it’s astoundingly good by itself, at least to my ears.  
The KLH Nine full-range electrostats I bought in 1991 from HiFi Classics in Far Rockaway, NY. $500 - and a major bargain! Still have them in occasional use along with the pair of Futterman H3aa OTL amps. 
My favorite is my pair of Watkins Stereo WE-1s speakers, they are large but have such a sweet musical sound, even at 37 years old. 
The ‘68 Les Paul Custom I lost in a burglary during college....still hurts.

After that, I’d have to say the Thiel 3.6’s.  I down-sized years ago, but I had a lot of joy thanks to Thiel.

Krell ksa100. All original. Getting it recapped this week after 30yrs. Can’t wait. 

Pioneer pl-630tt with ortofon black mm cart. Still works and sounds great. 
Things sure were made well back then. 
I’ve had quite a bit of gear come and go but my Janszen zA2.1 have remained and will always. The best electrostatic sound in a WAF friendly package.
Original Snell Type J speakers. I listened to more great music on them than on any other piece of equipment...still have them, but let's say they're retired.
On my best components I actually have two, one is a custom turntable made by Peter with PBN Audio and it sounds fantastic and it’s candy to the eyes.The other is a pass labs X A160.5 mono amps and I no longer own either of them I’m sad to say. My favorite piece is a recently acquired rel 812 sub and I am totally blown away by it, has excellent Impact without boom, spent a lot of time dialing it in but it was well worth it.

CEDAR DCX and CRX, invaluable in dubbing noisy old LPs. got 'em for a song on Ebay. one day i might spring for the DHX [dehisser]. 
First cartridge: NAD 9300, still have.

First receiver, Sherwood S9600 CP, still have.

Fist speakers, Polk RTA 12, still have.

First tape deck, Technics RM240X, still have.

Ive ADDED many components since 1981.
My powerfully powered
late model run 9/10 
Infinity IRS Beta speakers
Subwoofers and tweaks ?
Not likely !! 
My Audiomodded Sony SCD333ES 5 disc SACD player/changer. Still makes lovely music to this day, going on 16 years now!  Absolutely terrific sound, and without any harshness associated with CD's.  Really shines with SACD's.
Pioneer SX-1050. Has more than enough power to drive any of the JBLs I have had. Has all the input and outputs one could need.

As soon as I get my Pioneer TT back the 1050 will go into my 70s disco system.
Infinity Rennasiance 90 spekers.  Got a pair of spare EMIT tweeters just in case.  That case has never come up.  Had a spare pair of speakers "just in case".  That case never came up either so I offed them.  
Tandberg 3012 integrated amp.  Original owner since 1983. Has never let me down. Still strong and loud.  Controls my B&W speakers with ease. Great amp.  
Mark Levinson 23.5 amp and Magnepan 3.5R's.

I lost them when I lost my self to alcohol and the breakup of a relationship.  I fear they ended up in a dumpster.  Also my Lexicon MC-4 at the time and a dedicated HT in my own home.

I've lost lives, but sobriety is something no one can take away from me.
My Kyocera DA-610cx CD player. Purchased new in 1986. It's never needed service. It doesn't balk at playing newer file types like MP3's, FLAC's, etc. burned to CD-R's. The sound is warm and not overly bright.

Garrard 401 TT w/Scheu Tacco arm and Dynavector Karat cart, driving JLTi MC phono pre (w/custom umbilical from the designer, RIP).
Probably my Totem Arro loudspeakers. Fantastic imaging, tone/timbre, and bass response especially for the size and price.  High Wife Acceptance Factor, too.  I still own them but am not using them now. They were a bit undersized for the room and for some complex arrangements (or high volumes). Oh, and the Wife Acceptance is no longer a Factor.
My Aiwa AD F-770 three head cassette deck. 38 years and still going strong with nothing more than a belt change. Also, my Marantz st6000 tuner. These are the only things remaining from past systems.
IMO, once you achieved a very high level of synergy (including your ears/brain) it's VERY difficult, maybe impossible, to pick one single item in one's setup. 
How tricky is it, to chose between Burmester speakers, Levinson CD, DAC, preamp and PassLabs power amp?!? 🥴 
Am I the only one here with such a difficulty in answering the OP's question? 
M. 🇿🇦 
My favorite piece right now has to be a Lyra Kleos cartridge. I upgraded to a VPI Super Prime Scout but installed my old Ortofon cartridge. When I installed the Kleos, it didnt open the door to high definition sound it Kicked the door in with both feet. Couldn't be happier.