The following are known Action Replay Codes for Half Time on Nintendo Game Boy / Color (GB / GBC). These codes were also known as GameShark Codes and in most cases will work on both devices.

Device Compatibility: Action Replay & GameShark

P1 Score 100
916461c1

P1 Score 0
910061c1

P2 Score 100
916462c1

P2 Score 0
910062c1