The button layout of the AUXBOX from Bavaria is supposed to make it the most ergonomic fighting game controller.
The ST is a primarily stickless controller that is made of inox steel, has a see-through bottom panel, and glows in different colors.
It seems that DOIO took its creative liberties with the spacing of the KBGM-H03's buttons, especially the uppermost button.
The Mini•Dub is a smaller version of the 4TW by jonyfraze, and the primary difference is how the edges are mostly straight.
The VM6R offers multiple layouts and can be ordered as a case or preassembled. It also features both Iris & Lolli tech.
Chibico by Acrycade Gear is a mini stickless controller that should be able to fit into a back pocket of a pair of pants.
The QRD Maestro S3 can either work wirelessly or with a wired connection, depending on your preference when you play.
The Skullbox Leverless Arcade Controller is smaller & thinner than average and has proprietary SkullCaps that mimic the Sanwa feel.