Alien FPS Rig is a free first person rig for Maya based on a sci-fi theme (inspired by Alien). Made by Guillermo Moreno Alfaro.
Louise is a free high res facial rig for Maya, Unreal and Unity with a complete set of 236 blendshapes
Animate With Arran is a YouTube channel by Arran Baker who has recently started to post some great free videos around animation process, workflow tips and more.
Henry rig is a free rig made by students from Cogswell University
Built By Colossus Rigs are free and paid Maya rigs available for download. Founded and run by Roman Jeffery.
BOTW Link Rig is a free Maya rig based on the Breath Of The Wild version of Link (similar to the previously posted Zelda Rig). Made by Christoph Schoch.