There were a lot of accessories for the Commdore C-Serie, some from Commodore itself, some third-party.
Original Commodore Joysticks and Paddles
Citizen 2-color Printer for C64 and VC20
Eprom-Burner and -Deleter.
Disc-Holer for 5,25" Discs. With a hole in the disc the back (second) side of the 5,25" disc coud be written too.
Dataphon S23D with 300 to 1200 Baud.
Beginning of hacking ;-)