Last night I was shopping for that little Marshall practice amp online and one thing leading to another, I managed to trace back the first Marshall amp (not the actual amp, mind you) that I'd ever used.
 

 
Marshall Master Lead Combo like this one. It was actually my first real guitar amp - I'd played on crappy Radio Shack amps and rented ones up to that point. No tubes, obviously, but it sounded quite good as far as I can remember. Bought it used, can't remember how much it was. 
 
A few years later, I moved to Montreal w/ my first wife, money was pretty tight and I had just gotten my 59 Bassman, so I though I could do w/o the Marshall. I walked through the city from pawn shop to pawn shop carrying this thing on my shoulder. Because one of the pots was rather noisy, I got a big $50 for it. I didn't really have a choice but to take it at that point.
 
It's one of the few things I regret in my life. I'm never selling another instrument or amp again. Even my POD, I regretted selling - but later bought one back. And a little 10w Valvestate amp I sold, I ended up regretting it afterwards too - I'd cut some pretty cool demos w/ it. Living in an apartment, using the Bassman wasn't even an option. I remember doing all kinds of crazy experimentations to get different kind of sounds, putting the amp here or there, putting the mic in the back, throwing a comforter on it - anything, really...
 
It's actually one of the reasons why wanted to get the little practice amp - because I remember how much fun I had jamming w/ that thing - just a couple of knobs, no fx, no modeling, nothing.
 
Any piece of gear you guys wish you could have back?

I'm not even going to start... *Sigh*

craigb
I'm not even going to start... *Sigh*

 
This!

I guess somehow I'm fortunate enough to have played crappy gear for a big part of my life that most of it I don't really miss. Most of my guitars were bought by friends or given to them. One of them did a terrific job reworking my old Fender Squier. I remember him putting it back in my hands during a x-mas party a few years later and hooked me into that little Valvestate amp which he now owns too. I thought it was a pretty nice little rig. :)
 
 
 
 

I miss
 
my Rick
my first P-Bss
my EB-3 (not my EB-0)
every hoop shot I've eve made
 

I miss
 
all those brain cells I happily killed during the 80's...

64 Super Reverb, 59 Tremolux, 61 Princeton, 61 Deluxe, 68 Princeton, 69 Bluesbreaker. There's more, and I don't remember them all. Guitars I don't regret so much because I never had anything really outstanding. I only got the cool amps because I could fix them. Including the 72 & 73 Marshall 1959 heads and matching slant cabs. I could never get the volume above 1 or 2, who needs 11.

That's one sweet bunch of amps, John.
 
Oddly enough, my best amp probably was the 59 Bassman, but I don't find myself missing it as much as some others - unless I consider it as part of my rig at that time. On its own, I never played it much, bet it just for the simple fact that it was way too loud for my taste. It was for those loud band rehearsals and shows.
 
I like little amps. I guess it's something I'd like to do in the future - get a couple of small tube amps. 

I miss all my stuff that's still in storage in Denver, especially my '59 Shopsmith.

The worst part is it's not really gone. I just can't use it.

I hear ya...just before I moved out of home I bought what I think was the exact same amp, which was basically the biggest and most incredible amp I'd ever owned. And then I moved into a crappy apartment that needed doing up....and I had no money, and there were also a lot of parties coming up, so I sold it for a stupid chunk of stupid cash. God we're stupid when we're young. Having said that, it did throw me into the world of fingerstyle steel string playing, so I guess it wasn't all bad. 
 
EDIT: Now I think of it, I think mine was a Valvestate, possibly an 8240 (going by the size and wattage of the ones listed on the Marshall site) or whatever the equivalent was 22 years ago....