To enter the following cheats, the Z button is for the first slot, A button is for the second slot, and B button is for the third slot. Then end it with a direction on the control stick.

Effect Code
Tournament Mode (in a 2 team game) 1-1-1 Down
Show Field Goal % 0-0-1 Down
Punt Hang Time Meter 0-0-1 Right
Fast Turbo Running 0-3-2 Left
Huge Head 0-4-0 Up
Super Blitzing 0-4-5 Up
Hide Reciever Name 1-0-2 Right
Super Field Goals 1-2-3 Left
No Punting 1-5-1 Up
No Head 3-2-1 Left
Headless Team 1-2-3 Right
Big Head 2-0-0 Right
Big Heads Team 2-0-3 Right
Big Football 0-5-0 Right
Tiny Players Team 3-1-0 Right
No first Downs 2-1-0 Up
Allow Stepping Out-Of-Bounds 2-1-1 Left
Fast Passes 2-5-0 Left
Powerup Teammates 2-3-3 Up
Power-up Offense 3-1-2 Up
Power-up Blockers 3-1-2 Left
Power-up Defense 4-2-1 Up
Target Reciever (no highlighting) 3-2-1 Down
Always QB 2-2-2 Left
Always Reciever (requires human teammate) 2-2-2 Right
QB/Reciever Cancel Always 3-3-3 Up
No Interceptions 3-4-4 Up
No Random Fumbles 4-2-3 Down
Invisible (no affect) 4-3-3 Up
Turn Off Stadium 5-0-0 Left
Weather:Clear 2-1-2 Left
Weather:Snow 5-2-5 Down
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The followin cheats require both teams to agree (enter the same code)

Effect Code
Smart CPU 3-1-4 Down
No CPU Assistance 0-1-2 Down
Show More Field 0-2-1 Right
Power-up Speed 4-0-4 Left
No Play Selection 1-1-5 Left
Super Blitzing 0-4-5 Up
Hyper Bliz Mode 5-5-5 Up

Happy gaming =p