The following are known Action Replay Codes for NFL Blitz 2000 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

Always Have 1st Down
01014dc5

Always Have 4th Down
01044dc5

Team 1 Scores 0
010028C6

Team 1 Scores 50
013228C6

Team 2 Scores 0
010004C7

Team 2 Scores 50
013204C7

1sec left on clock
910151c5