Action Replay - Cheat device.



Sega Master System convertor - Allows Master System games to be played on a Megadrive.



Sega CD - RAM cart - allows external saving.



Random Cart Adaptor.



Game Genie - Cheat device.



Random Cart Adaptor.



Sega Master System Convertor II - Allows Master System games to be played on a Megadrive.



Pro Action Replay - Cheat device.



CDX Pro - Allows Sega CD games from other countries to work on whichever mega/sega cd you use. From what I've heard, it only works on Model 1 Sega/Mega CD systems.