A general favorite instrument is the Suzuki Humming Tremolo. Over time it has become clear that the Suzuki Humming is considerably more physically durable than quite a few others. It is more precise and repeatable in note and tone than most. One can get them in all keys major and minor, and at unusually low price, from The Musician's Webstore in Canada. In the U.K., Harmonicas Direct and The Harmonica Company are excellent sources. Rockin' Ron's has them in the U.S.
The Easttop T2406 and T2406S are very recent imports to English speakers, and are extremely interesting, professional grade, and very good price. Current reports have them best available from Dream-Harmonica through eBay, and secondarily through Amazon. We have solid reports that if you would like minor keys, or even a whole set of minors, Dream-Harmonica will provide on special request.
The Swan Professional is a relative newcomer. Good tone, strong construction, good durability, very good price, and joyfully, available in all major keys. I have purchased them at Tmart, and friends have purchased them from the Swan company's new outlet in the U.S.A. and reported excellent service. I think I slightly remember seeing this site in Chinese and wondering; perhaps I need to apologize for being linguistically challenged ☺ I do have to wonder how many of the other companies understand what Swan is producing. I think Suzuki has a clue; Suzuki Hummings are recently far more available in all keys major and minor than ever before. But the Swan Professional appears to be either almost as durable or just as, and prices much lower. More on this as experiences and reports accumulate!
The Hohner Echo Celeste still ranks well with some users. Many positive reports have been received. It has a very sweet tone, less volume than many. You will want a mike if you play one of these against anything or anyone amplified. There have been some very less-then-positive reports; current theory is that there have been bad runs of Hohner's mills for the Celeste. They are available from many sources, e.g., Musician's Friend in Kansas City, MO, in all major keys. Multiple reports have come in stating that if you ever do run into a bad one, Hohner will replace it cheerfully and quickly; thus far we do have one report stating the opposite. Price was originally advantageous for the Celeste, but this is no longer the case.
And we have the excellent and longstanding Tombo 1521, and Tombo 3121. The Tombo 3121 is available in all major keys and two minor; the Tombo 1521 is much more expensive, but with very good quality. You can find Tombo 3121, and Tombo 1521 Deluxe, from Harmonicas Direct.
definitely soliciting other good sources of tremolos, in every