The following are known Action Replay Codes for NHL 99 on Nintendo 64 (N64).

Device Compatibility: Action Replay & GameShark

Away Team Scores 0
810909380000
81092d600000

Away Team Scores 50
810909380032
81092d600032

Home Team Scores 0
810908fa0000
81092c700000

Home Team Scores 50
810908fa0032
81092c700032

Infinite Creation Points
800e73d900b0