I had a Matamp 2X12 that had a really "unique" sound. (This was a 120 watt chassis, the old 2000 model with an extra gain stage in the front. I don't think they make them anymore) I thought it sounded very dark, distant and was surprisingly "choked" sounding for what i thought would be a 120 watt monster. Definitely different...barky and dark. Weird amp. I thought it was too indistinct so I sold it to a friend who liked it. Different strokes.
Any single ended, large tube amp-Emery, Allen, THD
The Dano/Silvertone 3 tube (50C5, 35W4, 12AX7) and all their copies (you could say they're copies of the champ, but no champ ever sounded that ratty and lo-fi, or gave you such a shock if you weren't careful).
Kalamazoo Model 12-imagine a Princeton Reverb with more gain and less clean overhead.
Sansamp PSA1-oh wait, that sounds like ALL the others
I havn't even played squat of all the amps out there. I use a London power super standard and it can do all sorts of interesting stuff. So, I guess I'm missing out, but I do enjoy the amp that I use. I will be selling my others for lack of use, even though they do offer some cool tones. I do enjoy the discussions of all this though. I think I'd like to have a power scaled old Orange, that would be cool!
The Kelley sounds somewhat Fendery when clean, but really has a unique mid voice when driven hard in the attenuator channel.
Ampegs have unique sounds. VT40 is a unique piece. I love Ampegs when they are up loud. But I love almost any tube amp when it's up loud.
Orange Matamps have a unique sound, super detailed and wide frequency response in the clean part of the knob. Then in the middle volumes, a really unique loud sound that sustains prior to getting hairy. Above 7 they flood out into a really nice roar.
Old Marshall Superbass heads are different in a big way, from the normal grindy Marshalls.
I also think that the FTR-37 is more unique than credited in the opening post. Sorry there's no Deluxe Reverb that can approach tha racket and bottom end of the click channel. Plus the normal channel has twice the headroom, and at least twice the brawny bass. The distortion comes out of a totally different part of the note. That's how my ears hear it anyway.
This started its life as a Sovtek Mig 100. It now has EL34's and a massive output xfmr taken from a 140 watt Traynor bass head from the early 70's. The xfmr is so big that I could not mount it with the front panel of the amp on. It sounds great.
Orange - many models
Ampeg - several models (Gemini, R-e-R, V series)
Dumble - ODS 100
Fender - Tweed Champ
Mesa - Rectifier
These amps--particularly the Orange and Ampeg--produce sounds that I can often pick out because there's something different about their sound, and they haven't been emulated ad nauseum like so many others.
I think a number of the Divided by 13s and the Komet Constellation often sound like other amps but when you play them in person, they are capable of responding/acting pretty unique. I also think some of Alessandros are like that. The English can get an acoustic/hi-fi quality to it that's pretty unique.
We like to think all of our amps have a unique, original sound...but most don't, IMO. That doesn't make them bad or unworthy, it just means there harder to tell from some others.