Knockout Kings 2000 

Big head mode 
Pause the game:
and press C-Left, C-Right, C-Left(2), C-Right.
If you entered the code correctly, you will hear the bell ring five times. Repeat the code to disable.

Big gloves mode 
Pause the game:
and press C-Up, C-Down, C-Up(2), C-Down.
If you entered the code correctly, you will hear the bell ring five times. Repeat the code to disable. 


Hints 

Super punch 
Press A + B + R and the direction to punch while the glove in the upper corner is flashing.

Restore energy 
Move away from your opponent, hold Z and sweep the Analog-stick in circles. 
Alternatively, tap Z repeatedly without moving the Analog-stick.

Easy knockdown 
Fill your meter, then press R + L + A or B to knockdown your opponent 
regardless of whether he is blocking.

Easy training 
Select "Offense" in training mode:
Then, use the following moves to hit the blue opponent: Down + A, Down + A, Down + B, Down + B.
Repeat until he has been hit thirty times.