Here are a few and their functions. This adapter connects to Playstation units to allow for the addition of up to 4 more players when you get three more controllers. Nintendo 64 and Dreamcast consoles do not need this adapter as they have the ability to add 4 players already. This adapter connects to the controller slot. If your one of those players that tends to get stuck in a particular level, or runs out of ammunition too quickly while playing a video game Gameshark is for you.
Some people call it cheating and yet others call it beating the game.
There is one Gameshark for each console and games are given codes to be using with the Gameshark. Keyboards Some systems, like Sega Dreamcast, have built-in modems and can connect to the Internet for multiplayer gaming online. There are attachable keyboards where you could chat with other online players. Extension Cables PlayStation and Sega Dreamcast have extension cables for gamepads so you don't have to sit so close to the console you can sit on the couch or anywhere in the room. RFU Adapters You can use this adapter with many consoles they allow you to connect your video game system via RF wire rather than standard RCA wire.