GFS

GFS is the model format used by Atlus in Persona 5 and subsequent titles, such as Persona 4 Dancing All Night and it's successors (Persona 3 Dancing Moon Night and Persona 5 Dancing Star Night.) GFS format is usually used for (environment models), but in games like Catherine Full Body, it's used for character models too. Just like in GMD format, textures are embedded into the GMD file as a headerless variant of DDS format.

3DS MAX MAXSCRIPT
TGE created a maxscript that's intended to be used with Autodesk 3dsMax. It supports importing GMD meshes, rigging, materials, and even GAP animations. You can get it here. It currently does not support all animations or models with embedded EPLs used for particle effects.

GFD Studio
GFD Studio (formerly known as AtlusGfdEditor) is a tool for viewing and converting skinned models to GFS format. Rigging and mesh/texture conversion is currently possible, as well as manipulation of material properties. GAP files are also supported, so you can import, export, replace and re-arrange animations within them. You can download the latest build here.