There was the BHP virus, but that was more of a proof of concept, and I don't remember hearing much (if anything) of it being in the wild. That said, it could stamp itself on disks even by simply listing the directory. 64'er was indirectly its source (by claiming it couldn't be done), and they were also the ones to issue a cleaner to remove it from disks.

See also groepaz's list: https://hitmen.c02.at/files/docs/c64/C64_Virus_List.txt