Gradius Collection Cheats

Gradius Collection Unlockable: Stage Select
Finish the game.

Gradius Collection Hint - Save Farming
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.

Gradius Collection Unlockable: All Power-Ups

To unlock all power-ups (including weapons), try inserting the famous "Konami Code" while the game is paused. In case you don't know (or remember) the Konami Code, here it is: Up, Up, Down, Down, Left, Right, Left, Right, L, R.