Charles Bay mouthpieces are among the most unknown and underrated mouthpieces produced today. Very difficult to find, however, ProWinds in the USA stock a few, including the fabulous ligatures. Charles Bay bought MC Gregory's equipment from Gregory's daughter, Gale. Charles Bay and his son still hand-finish and play-test their mouthpieces, which are among the very best contemporary mouthpieces.
Note added July 2018: Charles Bay passed away last year or earlier. Lots of molds and mouthpieces from his estate has been sold. Morgan mouthpieces acquired the molds for the MC Gregory mouthpieces.

Bill Street is a saxophonist from University of Southern Maine who occasionally makes mouthpieces, mostly for clarinet. They are very rare and play very well. Read more here.

Meyer alto mpc modified by Matt Marantz. This is what the owner wrote to me about the mouthpiece:

It is definitely one of the best Meyers I’ve ever played! It shares the same qualities as my “top 5” Meyers: superb response across registers, very quick articulation, stellar intonation, punchy and powerful, warm and with “belly”, focused core, reed-friendly, and an inherently flexible sound to work with. It also just gets out of the way and lets you fill the horn with sound and melodies.
However, he decided not to keep it after he had played it live (He normally plays larger tip openings):

I actually had real gig this weekend and while the Marantz Meyer plays fantastic in the practice room, it is definitely too small for me when I’m playing live (in the heat of battle I seem to push harder and use more air volume).

MC Gregory / Gale
. Gale was Gregory's daughter. Read about these mouthpieces, their opening codes etc at Theo Wanne's site. What Theo does not specify, is the lay length: "B" is long facing, "A" is medium, and " " (nothing) is short facing.
Paul Desmond seems to have played both the Model A and the Master model on his alto saxophone.

Meliphone /Wood Wind Company. I found the following on Sax on the Web Forum:
The Woodwind Company, founded in 1919, was managed early on by Eugene Bercioux, a French native living in New York City. Bercioux' name is on U.S. Patent No. 1,452,953, granted in 1923, for a mouthpiece facing machine. The patent number appears on many WWCo mouthpiece blanks.
The Steel Ebonite tradename, much like C.G. Conn's Steelay tradename, referred to an extra-hard rubber compound. It is not known whether it contained steel shavings, altho it has been compared to bakelite and may have contained same. Once Leblanc took over the WWCo trademarks it was renamed Steelite Ebonite.
Types B, C (solo jazz), D, G, and K (section lead) were all available for clarinet. G was the favorite symphonic model, but was also used at least briefly by Benny Goodman.
Types B, C, D, G, K, and N were available for saxophone. C was the jazz alto model, N the jazz tenor.
Tip openings ranged from 4 to at least 9 (perhaps 10), including starred numbers 4*, 5*, etc.
The B series was apparently the working pro favorite in the 1930s, but by the '50s it was the K.
WWCo also did models like the '36, the Meliphone (straight sidewalls, steel shank band), the Sparkle-aire (brighter sound), and the Educator (student model), as well as "player endorsed" models for Dick Stabile, Chester Hazlett, Robert Marcellus, and Joe Crossman. Stabile's pieces were Meliphone K5s.
There were also WWCo metal pieces, mostly for tenor apparently. I missed out on purchasing one recently, but they're said to be as good as the others. The blanks were used by other makers as well.
WWCo facings sometimes appear on other makers' mpcs, too. You could go to their NY shop and have refacing done, and they would stamp the table like one of their own pieces.
WWCo sold out to Leblanc in 1968.
An advertisement (from 1956 ?) can be seen here: http://www.ilsaxofono.it/portale/articoliimboccature/352-bocchini-woodwind.html

Mouthpiece Café. Brian Powell and Erik Greiffenhagen are both educated in mouthpieces and their refacing by the late Ralph Morgan. Erik Greiffenhagen still manages the Morgan business. Like the Morgans, the Mouthpiece Café mouthpieces are carefully finished and playtested so they all play without any flaws. Highly recommended.

Rico Royal (Metalite Graftonite.) These mouthpieces were the last of Arnold Brilhart's constructions, and of which he was very proud. He had managed to create a mouthpiece that could be mass produced and did not require any finishing afterwards.
This made it possible to sell these at a very low price. Contrary to the intentions, most people believed that they were no good because of the low price. That is a pity because they are very good playing and sounding mouthpieces. The Metalites are much desired by people in the know, especially for baritone and tenor sax. Due to popular demand, Rico has recently started producing the Metalites for tenor and soprano again.

Santy Runyon was a legend in American saxophone history. A great player, inventor and teacher. He helped several jazz greats develop their technique, including Harry Carney and Charlie Parker. His Custom mouthpiece and the SR model are very good mouthpieces with a unique sound. Charlie parker played his "22" model for a long period. The Runyon mouthpieces made today are of the same high standard as always. It is worthwhile to visit Runyon's website.

Vito Pascucci was instrument repair man for Glenn Miller's band. After 2. WW he started importing saxophones and accessories to USA from France and later Japan and Taiwan. His saxophones have always been of very high quality despite being sold as low price student instruments. His mouthpieces are very good players and of a quality much higher than their price.

Wolfe Tayne. Wolf Taninbaum was a CBS and NBC staff musician who also performed as a solo artist with orchestras such as Benny Goodman, Jimmy Dorsey and Les Brown under the stage name Wolfe Tayne. Striving for the perfect sound, he developed saxophone reeds (among them the first synthetic reeds in 1952) and mouthpieces. Some of his unique mouthpiece facings were applied to Otto Link blanks, which are the desirable ‘W.T.’ Otto Link models.
He worked with Ben Harrod at the Link factory in Pompano Beach, Florida and are, together with Harrod, responsible for the fabulous Florida Links.
While he worked there, he began producing saxophone mouthpieces under the trade marks Wolfe Tayne and Guy Hawkins. The Guy Hawkins mouthpieces were intended to be darker sounding than the Wolfe Taynes. His first mouthpieces had the tip opening marked on the table. These are very fine pieces of high quality, easy playing and with a full sound. Later, the tip opening was stamped to the right of the table, like on Florida Links. The last had the tip opening on the shank. Those may have been made after he sold the companies to Babbitt. Later he founded the Bari company in Ft. Lauderdale, Florida. Again, the playability and sound of the mouthpieces were in a class by itself, as long as made while under his supervision.