Metal Slug 3 Cheats

On the first mission after the boat hits the pier stay on the boat then a crate will break and there will be a tank inside. jump in it and move it towards the pier. when your close to the pier press the a and the tank will do a leap in the air onto the pier. if your to slow you will die cause the boss will come out where the boat is.

This isn't really a code or a cheat but when your playing and you have
zero lives and your about to die push start on the other controller and
the 2cd player will come on. Let your other person die and play with the
new one. If you don't have a extra controller it wont work or at least
no one knows how to yet. This really works good when your on the last
level.

The level containing the zombies has a secret and unique area. About the end of the middle part of the level, you will see a sign above a frozen-shut cave reading "ICEMAN". Walk to the left to go over here and shoot the ice wall blocking the entrance. Inside are numerous "ice men" and at the end of the cave is a buried Elephant Slug, frozen in the ground which you can free and ride.

Completion bonuses:
To unlock the Chubby Isle Paradiso (Fat Island) and Storming the Mothership (UFO) options at the Main menu successfully complete and save the game on Normal difficulty.
Continue game play:
To continue the game with the same player after losing all your lives press
Start on controller two.

Complete the game on normal difficulty

When your down to your last life on arcade mode press start on controller 2. This starts you off on player 2's controller when your in a tough spot, giving 3-5 new men. This is helpful for Mission 5 or some of the harder bosses. If you're quick enough you can die on the player 1 controller and press start on controller 2 and still continue. The only flaw to this is you wont be able to select the same character you had as player 1.

Complete the game to unlock Storming the Mothership amd Chubby Isle Paradiso.