Guild bluesbird guitar from the 1970’s.
I stupidly sold it because the neck was a bit too slim but I’ve never seen another one like it anywhere and it was an amazing sounding guitar, no fret buzz and amazing resonance and sustain.
Shergold Meteor guitar.
This was my baby for 23 years but I’d got some better guitars and it got overshadowed and I wasn’t really playing it so I let it go and I should have hung onto it because it had a certain magic about it.
Moog MF103 phaser. I can’t even remember actually selling it but I was at a time in my life when I’d kind of given up on making music and was focused on other things but I want another one and they aren’t cheap now.
Morley Foot Phaser
Another very good phaser, totally overbuilt, heavy chrome like a Dualit toaster. Off the charts build quality and I sold it for less than it was worth.
EH/Sovtek Small stone Phaser. Not only built like a tank but possibly even made from bits of tank and dark green. Selling for a lot more now than what I paid for it.
Alesis quadraverb +. Didn’t realize I’d ever want it again and now the prices have risen somewhat.
Atari Mega ST4. Dad wanted it out of his loft and at the time I didn’t think I’d ever want to use it again. I had the genuine Cubase software and a bunch of floppies. A rare-ish Atari and I would love to have it back… another dumb move.
In some ways I regret selling almost all of the things I’ve sold as there is a sense of failure that I either didnt give things a fair crack of the whip or sold because of self manifested guilt over underutilisation. I don’t think about this much though - life’s too short.
But I do regret selling a Monomachine mk2 with plus drive (that I bought and sold for like £500 or sometime stupid) and a Yamaha FS1r.
my cheap nylon string classical guitar
it was my first instrument, and it feels like im missing a small part of me ever since
regret is not the right word. i just miss it sometimes. hope its doing well 
MFB Dominion 1
Alpha Juno
Sherman Restyler
And maybe the Oto Biscuit, even though i wouldn’t use it a lot. But it’s such a rare item now.
Nord Lead 2
Jomox XBase 888
Virus B
Polara Reverb
Obscura Delay
Would like to still have the Oberheim DX I sold for £200 over 15 years ago. Prices for them are silly now (damn New Order fans!) so buying one again is off the cards.
Two things, original EHX polychorus and Ensoniq SQ-80. I’d probably go for another SQ-80 if I found one nearby…
How about stuff you regret buying?
For a while I regretted selling my Digitakt and SP-404sx, but time heals all wounds 
My '79 fretless Musicman Stingray. Notice I still say “my.”
Sold it after a divorce, of course. Don’t regret the divorce though.
I had a dream about the Digitone keys that I used to have. I am hoping for a Digitone Keys II to be released someday.
One of my children.
Sequential Studio 440
Sequential Tom
Roland TR-808
Roland TR-909
Emu SP-12
Emu SP-1200
Akai MPC-60
Akai MPC-3000
Elektron Monomachine
Elektron Machinedrum
WMD Geiger Counter Pro
I sold and bought the Arturia sparkle, 3 times over a span of 10 years. That stupid little controller and outdated vst, makes me so happy. This time I am keeping it.
Novation circuit rhythm, sold and bought 2 times. Moved on to a TE KO2, still miss the rhythm.
I really miss my Yamaha rs7000.
One should not sell one’s children.
Should have given them away 
Jokes apart, I realize reading this through that I never regreted anything based on “look how expensive it is now!”. It’s more about “I miss playing it/having it around” to me… but knowing they make someone happy makes me kind of happy. Must be emotional.
Roland GR100 hex fuzz
I miss my second hand AR MK1 that I got for a good price. It was probably my favourite little groovebox ever. It was not perfect, but the analogue filters make boring loop pack samples sound great and I love the MK1 form factor. When I got one for £550, it was a bargain. I should have never let it go, the price-to-fun ratio was amazing and it worked great with a tiny knobby MIDI controller to control the performance macros.
I have often wondered about picking up a cheap used A4 MK1 to give it a spin.
Also, I like 16 buttons in a row MUCH more than 2 rows of 8. Seriously!
Roland TR-808
LinnDrum
Roland Juno-106 in mint condition
Roland MKS-70 with PG-800 programmer
Yamaha FS1r
That’s it.
Edit: also my Boss PH-1r phaser pedal.
sometimes i miss the Korg DW-8000 I sold.
j
0=0
Compared to the gear purchased throughout the decades, I have not sold many items. Below are three items I later wished were kept, however:
- Yamaha RS-7000
- Roland V-Synth
- Emu E4XT Ultra