Gradius 3 is a whole lot like the first Gradius game. So you might think that you can use the old Konami Code to get a munitions boost like you did in the earlier game. So you pause the game, put in the code
Up, Up, Down, Down, Left, Right, Left, Right, B, A
and notice how you get all the powerups, just like before, only when you unpause the game:
Your ship explodes!
I guess it's kind of an acknowledgment of the old code or something.
But, you can slightly modify the code. Instead of pressing Left and Right on the control pad, you can press the L and R shoulder buttons on the controller.
Up, Up, Down, Down, L, R, L, R, B, A
Which will have a similar effect as the original code did for the original game.
And, just like the original code, you can only do it once per credit, so choose wisely.