Ikaruga Cheat Codes for Gamecube

Chain Counter
To toggle on a chain counter which appears beneath the Chain Status box, press Z at anytime during gameplay.

Gallery 1
Play the game for 5 hours or complete the Trial Mode without continuing

Gallery 2
Play the game for 10 hours or clear the game on any difficulty setting.

Game Mode Option
Play the game for 20 hours or beat the game on Normal without continuing.

Game mode option
Successfully complete the game under the normal difficulty setting without using any continues to unlock the "Game Mode" option at the "Appendix" menu. Alternately, accumulate at least twenty hours of total game play.
Submitted by: Tamera

Control two players at once
Note: This trick requires two Wavebird controllers. Set the receivers on the same channel and use one Wavebird on the same channel. You can then control two players at the same time. Set them side to side (horizontal) or (vertical) above each other by pushing them to the edges of your screen. If one gets wasted, you can quickly change color so you will have one black and the other white.
Submitted by: Tamera

Increase score permanently
Every time you continue, the last digit of your score goes up by one permanently. For example, if you continued once it is a "1", twice for a "2", etc. This is useful for gauging how much you have continued once the "Free Play" option has been unlocked.
Submitted by: Tamera

Sound Test
Play the game for 15 hours or beat the game on Easy without continuing.