F-Zero GX cheats and cheat codes for Gamecube

Unlock AX machine parts
Finish the game in story mode on hard mode.

Unlock AX tracks
Win 1st place on the F-Zero AX arcade track and save your game 
to a memory card or beat all of the grand prix tracks on the 
Master difficulty level.

Unlock AX Cup in Gran Prix mode
Unlock all the F-Zero AX tracks

Unlock all AX racers
Finish the story mode on the very hard mode.

Finish Story Mode chapter #1 on very hard: Unlock Phoenix/Rainbow Phoenix
Finish Story Mode chapter #2 on very hard: Unlock Princia Ramode/Spark Moon
Finish Story Mode chapter #3 on very hard: Unlock QQQ/Rolling Turtle
Finish Story Mode chapter #4 on very hard: Unlock Don Genie/Fat Shark
Finish Story Mode chapter #5 on very hard: Unlock Digi Boy/Cosmic Dolphin
Finish Story Mode chapter #6 on very hard: Unlock Dai Goroh/Silver Rat
Finish Story Mode chapter #7 on very hard: Unlock Dai & San & Gen/Pink Spider
Finish Story Mode chapter #8 on very hard: Unlock Lily Flyer/Bunny Flash
Finish Story Mode chapter #9 on very hard: Unlock PJ/Groovy Taxi
Finish all missions on very hard mode: Unlock Magic Seagull

Unlock Deathborn's vehicle
Finish the game in story mode by completing all chapters

Unlock the Bahumut vehicle:
Go to the F-Zero AX arcade machine and use your F-Zero GX License Card. 
Save the data that is unlocked to a memory card.

Unlock AX Mute City - Sonic Oval track
Win 1st place on the AX cup.

Unlock the Sounds of Big Blue:
Win all cups in Master mode.

Hear the unlocked character theme songs during replay:
Press L or R trigger during a replay to change the music.

Easy drift turn:
To perform an easier drift turn, quickly press Right, Right or Left, Left
Note: Not work in slide turn.

Unlock hard difficulty level in story mode
Finish a Story Mode mission and it will be available for that mission

Unlock very hard difficulty level in story mode 
Finish a Story mission on Hard and it will be unlocked for that mission

Spade 
Finish all story mode missions in hard mode

Unlock character FMV sequence on profile screen 
Win any cup on Master Class using their machine 

Master Class 
win 1st place in the Emerald, Ruby, Diamond and Sapphire cup in Expert mode

Get the Diamond Cup 
win 1st place in the Emerald, Ruby and Sapphire Cups on the standard difficulty
or
win 1st place in the Emerald, Ruby and Sapphire Cups on the Expert mode

Unlock the AX Mute City Sonic Oval 
Win the AX Cup. 

Show subtitles in story cutscenes
Hit the Z button during the cutscene.

Split Oval Staff Ghost 
Complete the Casino Palace: Split Oval in time: 1'07'00 

Twist Road Staff Ghost 
Complete the Mute City: Twist Road in time: 1'10'00 

Unlock New Mute City Music:
Go to the F-Zero GX Shop, then push the following buttons combination: 
X, X, X, Y, X, X, X, Y, Z, Z, LEFT, RIGHT, LEFT, RIGHT, LEFT, RIGHT 

Non-tested cheats:
Emerald Cup score passcode:
Choose time attack, then select the "Records" option. Select Emerald Cup and 
highlight the score to be posted. Hold R trigger and push Z, A, C-Down, L, C-Left, 
A, Z, C-Left, L, A buttons on your controller to get a password for that score 
to be posted on the rankings site. 

Ruby Cup score passcode:
Choose time attack, then select the "Records" option. Select Ruby Cup and 
highlight the score to be posted. Hold L trigger and push R, A, Z, A, C-Up, C-Left, 
A, C-Down, R, Z buttons on your controller to get a password for that score to be 
posted on the rankings site. 

Sapphire Cup score passcode:
Choose time attack, then select the "Records" option. Select Sapphire Cup and 
highlight the score to be posted. Push L, A, L, A, C-Up, L, C-Right, A, R, C-Up 
buttons on your controller to get a password for that score to be posted on 
the rankings site. 

Purchase sounds Of Big Blue in the shop for 99 ticket:
Go to the F-Zero Shop, then jump to the machine parts/items screen and enter the 
following cheat code by using buttons and the d-pad on your controller: 
Z, LEFT, LEFT, LEFT, Z, Y, X, Z, LEFT, RIGHT, LEFT, RIGHT, Z, X, Z, X, Z. 
If the code is accepted, you will hear a sound.

Activate Big Blue track:
Highlight any Big Blue track in Practice or Time Attack mode and press L 
trigger.