Gradius Collection Cheats (PSP)

Pause in any game on the easier difficulty setting, then press Up(2), Down(2), Left,
Right, Left, Right, L, R to unlock all weapons and power-ups. In the Japanese version of
the game, press Up(2), Down(2), Left, Right, Left, Right, X, Circle.

This is not necessarily an awesome cheat, but it is something that I happened to stumble
upon while playing.  Thus far, this code has worked for Gradius II so I imagine that it
will work for all of the games.

Basically, get a few power-ups, and then save your game.  After saving, load your game
and you will notice that the power-ups that you earned are still there.  So, if you keep
doing this, you will eventually have a full arsenal.