Hi Folks,
Everyone knows you can do this with emulators, but let's list the devices that let you do this on the real hardware!
NES:
Game Action Replay
Game Master (famicom)
SNES:
Game Saver
Genesis:
?
Gameboy:
?
Other systems?
Evrybody knows about gamesharks and game genies, etc. but let's talk about these!
-Rob