From Wiki - GameHacking.org
The Game Killer is a Game Enhancer for multiple consoles. The casing for the Nintendo 64 version shows that it is simply a repackaged Nintendo 64 Action Replay Pro. Datel Game Products is also credited on the packaging for both releases.
- PlayStation - A PlayStation memory card which has cheats built in. Rather than using actual cheat codes, it probably was a multi-page memory card that made use of Power Saves. The button on the card probably switched the pages and the light in the middle probably changes color depending on the page in use.
- Nintendo 64 - A cart with a timer built on it, much like the Nintendo 64 Action Replay.