Guilty Gear X

Change to 5th costume palette
Go to the fighter selection screen, highlight a character
and press Select

Change to 6th costume palette
Go to the fighter selection screen, highlight a character
and press A + X

Change to 7th costume palette
Go to the fighter selection screen, highlight a character
and press B + Y

Guilty Gear mode:
Finish the arcade mode with all characters.
or
Finish level 100 in survivor mode.

Unlock Testament as playable character:
Reach level 20 in survivor mode and Testament will
be your opponent. Defeat Testament to unlock him.

Unlock Dizzy as playable character:
Reach level 30 in survivor mode and Dizzy will be your opponent
Defeat Dizzy to unlock her.

Unlock character's ending:
Finish arcade mode with any character without using a single
continue to view character's ending.