Does anyone know of good online shopping sites where I can buy old, rare video games or Cheating Devices?

I've been looking for a video game site where they have old and rare games (like PS1, Dreamcast, Sega Saturn, ect.) because they don't sell them in stores anymore, nor do they sell cheating devices either (Gameshark, Code Breaker, Action Replay, ect.). Anyone have any ideas?