Ikaruga

Enable chain Counter
Hit Z during game play.

Unlock Gallery 1:
Beat Trial Mode without using a single continue
or
Play with the game minimum 5 hours total.

Unlock Gallery 2
Finish the game on any difficulty level
or
Play with the game minimum 10 hours total.

Unlock Sound Test option in the Appendix menu:
Complete the entire game in easy mode withouth using a single continue
or
Play with the game minimum 15 hours total.

Unlock Game Mode Option in the Appendix menu:
Finish the game on Normal mode without using a single contine
or
Play with the game minimum 20 hours total.

Getting the Dot Eater! ranking:
Finishing a stage, but do not fire the Ikaruga even once.

Unlimited continues:
Play with the game minimum 7 hours total.

Make the pause menu disappear:
Hit start during game play to bring up the pause menu.
Hold X and Y at the same time and the pause menu will dissappear.