Fight Night: 2004:

Unlock All Venues:
On the Main Menu, select My Corner and enter the following:
Left, Left, Left, Right, Right, Right, Left, Right, Right.

Big Heads:
On the Main Menu, select My Corner and enter the following: 
Left, Right, Left, Right, Left, Right, Left 

Unlock Big Tigger:
At the Main Menu, select My Corner, then Record Book then Most Wins-Boxer, then press Up twice.

Midget Mode:
At the Main Menu, select My Corner, then Press Left, Right, Left, Right and Left.

Bolo Punch:
Defeat Ray Leonard to unlock the Bolo Punch. 

Ducking Hook Punch:
Defeat Muhammad Ali to unlock the Ducking Hook Punch. 

Look Ma No Hands Punch:
Defeat Roy Jones Jr. to unlock the Look Ma No Hands Punch. 

Lunging Hook Punch:
Defeat Bernard Hopkins and Evander Holyfield to unlock the Lunging Hook Punch. 

Watch the Birdie Punch:
Defeat Bernard Hopkins to unlock the Watch the Birdie Punch.