International Super Soccer 98
Overhead Pass
First start running with the stick and the dash button. Release them both and press the left C-button. The player will pass the ball over his own head. This is an excellent way to avoid defenders.
Credit Goes To: Benjamin Dover via IGN 64

Big Head Mode
Wait for the words "Press Start" to flash on the title screen. Now press C-Up, C-Up, C-Down, C- Down, C-Left, C-Right, C-Left, C-Right, B, A. Now hold the Z button and press Start. You'll hear the announcer shout to confirm the code.
 Overhead Pass
 Big Head Mode
 Bonus Heads
 Bonus Teams
 Diving
 Juggling & Tricks
 Mardona Spin
 Play As World Stars
 Rotating Heads
Bonus Heads
Complete the International Cup on Level 4 or higher. Once you have viewed the end sequence go to create player. At the "head select" screen press the Left Shoulder button. This will take you to page 11 and a selection of strangely unusual heads.

Bonus Teams
At the "Press Start" screen press Up, C-Up, Up, C-Up, Down, C-Down, Down, C-Down, Left, C-Left, Right, C-Right, Left, C-Left, Right, C-Right, B, A, then hold Z and press Start.

Diving
When your player gets tackled and doesn't fall, immediatly press a direction on the D-pad + the one-two pass button, the through pass button, the shoot button and the cross button simultaneously.
If done correctly, your player will dramatically throw himself on the floor and claim a foul. Beware though, do not perform this manueuver close to the referee as he will book you.

Juggling and Other Tricks
While you are in training, or in a game, press and hold C-Left. The player will start doing tricks, such as rolling the ball up on his foot and juggling it around on his knee and feet and head. Different players have different tricks.

Mardona Spin
While playing, get the ball on offense. Using any player, push the DASH button to perform a dash. During the dash, rotate the control stick 360 degrees to execute a Mardona spin.

Play As World Stars
At the title screen press Left, C-Left, Right, C-Right, Left, C-Left, Right, C-Right, Down, C-Down, Down, C-Down, Up, C-Up, Up, C-Up, B, A then hold Z and press Start. Be sure to use the d-pad to enter directions.

Rotating Heads
At almost any menu which features a player's picture press and hold C-Up then press Z or L to rotate the face to the left, or R to rotate the face to the right.
Credit Goes To: IGN 64