Gradius 3 seems to be quite uneventful as far as unused junk goes. I haven't found anything yet and I'm more than halfway through the game. However, I did, for the first time ever in my life, manage to get into and complete every hidden bonus area. Man, you can skip a good portion of the game by doing that. Once you're in a bonus area, as long as you don't die, you'll skip the boss of the stage you were in. The only bonus stage that's hard is the first one because that one has walls that materialize out of nowhere, but the other ones do not.