NFL Blitz
Quarterback's View
While playing, choose any passing play then jump out bounds. While their, throw the ball. If done right you will see the quarterback's point of view.

When you are at the match-up screen (the screen where the announcer announces the teams that are playing). Press Z, Z, B, B, B, B, B, Up. This will access the blood code.
Credit Goes To: Christopher McCandlish via IGN 64

 Quarterback's View
 No Shoes
 Extra Blocker
 Hide Cursor
 Bonus Players
 Cheat Codes
 Weather Change
No Shoes
When the announcer says "Who's Playing?", enter the following code: Z, Z, B, B, B, B, B, B, B, A, A, Up and your team's players will not have shoes.
Credit Goes To: Adam Cornelisse via IGN 64

Extra Blocker
To have an extra blocker press both pass and hike buttons (A and B by default.) This makes the the person that goes in motion block.

Hide Cursor
To hide your cursor when picking a play,press up on the control stick twice. This makes the cursor diseappear and prevents the other player from seeing your play.
Credit Goes To: Gram ( via IGN 64

Bonus Players
Enter these codes at the Enter Initials screen.

Name      Code
Julia     1234
Turmell   0322
Sal       0201
Jason     3141
Jenifr    3333
Daniel    0604
Japple    6660
Root      6000
Luis      3333
Mike      3333
Gentil    1111
Brain     1111
Forden    1111
Skull     1111
Carltn    1111
Shinok    8337
Raiden    3691
Thug      1111
Van       1234
Billz     0526
Zz        1221
Jimk      5651
Marka     1112
Ed        3246
Todd      1122
Mitch     4393
John      5158
Josh      4288
Ryan      1029
Beth      7761
Brian     0818
Grinch    2220
Paulo     0517
Lt        7777
Nico      4440
Gatson    1111
Guido     6765
Rog       8148
Monty     1836
Shun      0530
Gene      0310
Paula     0425
Dbn       6969
Thug      1111
Cheat Codes
Enter these codes on the Matchup screen.
Big Players       1-4-1 Right
Big Head Team     2-0-3 Right
Fast Passes       2-5-0 Left
Headless Team     1-2-3 Right
Hide Name         1-0-2 Right
Huge Football     0-5-0 Right
Huge Head         0-4-0 Up
Hyper Blitz       5-5-5 Up
Hyper Turbo       3-2-0 Left
Invisible         4-3-3 Up
Invisible Qback   3-4-2 Left
Late Hits         0-1-0 Up
More Speed        4-0-4 Left
Night Game        2-2-2 Right
No CPU Assistance 0-1-2 Down
No First Downs    2-1-0 Up
No Fumbles        4-2-3 Down
No Head           3-2-1 Left
No Interceptions  3-4-4 Up
No Out Of Bounds  2-1-1 Left
No Punting        1-5-1 Up
No Random Fumbles 4-2-3 Down
Power Blockers    3-1-2 Left
Power Defense     4-2-1 Up
Powerup Blockers  3-1-2 Left
Powerup Defense   4-2-1 Up
Powerup Offense   3-1-2 Up
Powerup Speed     4-0-4 Left
Powerup Teammates 2-3-3 Up
Random Plays      1-1-5 Left
Show Field Goal % 0-0-1 Down
Show More Field   0-2-1 Right
Smart CPU         3-1-4 Down
Super Field Goals 1-2-3 Left
Tiny Players      3-1-0 Right
Turn Off Stadium  5-0-0 Left
Unlimited Turbo   5-1-4 Up
Weather Change
Enter these codes on the Matchup screen.
Clear Skies  2-1-2 Left
Rain         5-5-5 Right
Snow         5-2-5 Down
Fog          0-3-0 Down
Thick Fog    0-4-1 Down
Credit Goes To: IGN 64