EVO (cosmetic replacement of the Egg, since Fordians do not hatch from eggs but are rather born as this larval template form, which will evolve into the basic form of its species once it gains enough experience by observing and learning about the world around it. EVO is an acronym of Embryonic Viscous Organism.)
Trojent and Ratkit
Renby, Rengon and Renlong
Pupart (R), Scolpendum and Mega Scolpendum
Seephysis, Sylpine and Splintaur
Kindlen, Marblaze and Characal
Aquett, Seacada and Mermantis
Skiteracha, Blattalion , Cucaradix and Ramboach
Skiteracha is genderless
Blattalion is always female
Cucaradix is always male

Skiteracha's evolution into Blattalion or Cucaradix is determined by personality value; this is done as a workaround to the current lack of gender-based evolution in Gen III. It evolves into Ramboach with a Leaf Stone.
(Ramboach's gender ratio is 50/50.)
Shatai (Female)
Mechaton, which comes in two subspecies (one a Steel/Dragon type and one an Ice/Dragon type)
Hei, Hilo and Helachnea
Hemomerus and Hanswig
Psyder and Psytic
Pupart (G) and Garyunoko (I plan on adding a Mega Garyunoko)
Tetshroom

Funny story with this one, one time I launched my game and the very first thing I encountered was a shiny Tetshroom. I recorded my reaction which is hilarious but didn't upload it anywhere yet.
Stahlarch
Skiblade and Aeroblade
Galverodon and Cynapse
Chibird and Nekowl
Carbutane
Some Mega evolutions to Fordians that aren't original designs in their base forms
Polteroak (Female)
Stahliken
Lunavian
Laytonium (Female)
Greaskito (Female)
Zorslash (Female)
Clamporo, Horachen* and Zorachen (Horachen is so far the only direct sprite sheet reuse from the old, terrible hack)
Eurekren
Naruhouou (Female)
Electronoa
Jormundarr
Pegi and Hadesus