An artist on Deviantart named DarkHedgehog23 and his group are making Sonic the Hedgehog models for SFM and Gmod, but they're pretty backed up, and he's made some of his projects available for download, in case anyone wants to download them and finish them up. Some notable ones include:
https://www.deviantart.com/darkhedgehog ... -566084323
https://www.deviantart.com/darkhedgehog ... -567310035
https://www.deviantart.com/darkhedgehog ... -564877253
https://www.deviantart.com/darkhedgehog ... -567222704
If anyone has any SFM or Gmod porting skills, or skills with getting 3D models rigged and UV-mapped, please let him know you're willing to help.