I’m a fan of Shihab Meboob’s, you might say - Aviary and Mast are the most innovative social clients I’ve ever seen. I’m also a bit of a collector of text manipulation applications like Texcraft, of which there are just a few that are truly comparable on iOS. On macOS, there really aren’t any equivalents at all.
For someone like me - who uses Textcraft’s transformations both recreationally/socially and has used them in development-ish tasks - its $4.99 and featherweight 3.7 MB were/are more than worth the experience. It’s super configurable, capable, and robust.