Wasn't there a hardware Gameshark that you could plug into your Playstation?
Update, I found the one I gave Charline, it plugs into a parallel port on the older Playstations.
So, there's a CD version, and a hardware plugin.
__________________
-Dreams of getting a new 360 XBOX in 201x.
-Current consoles: Playstation 2 and Wii, also has DS/GBA and a PSP 3000
-PC: AMD 5000 2.6 Dual Core, 2GB Ram, 8600 GeForce GT video card, SB Live!, Win XP SP3