Note: this secret only works in Battle Mode while you are a Revenge Bomber. Say "Dangerous Bombs" into the mic on the DS and you will have Dangerous Bombs that explode in a 3x3 square.
Bomb Up: Increases amount of bombs that can be dropped by one (maximum of eight).

Increases speed by one level (maximum of eight).
Increases firepower of bombs by one level (maximum of eight).
Increases firepower to maximum automatically (maximum of eight).

It is possible to save important items for the next level, such as glasses or the firesuit.

Kick a Rubber Bomb into a Dangerous Bomb. This may also work with other kind of bombs.

You can also kick two Rubber Bombs. They will both hit each other and make a Super Danger Bomb.

Equip either the Invincibility power-up or the Fire Suit. It is also recommended to equip some Speed-Ups, Bomb-Ups and Flame-Ups for the trick to be more effective. Plant a bomb and stand next to it, waiting for it to explode. Meanwhile, repeatedly tap A to plant a second bomb in the blast, then another, and so on. The process should continue forever. Having the Bomb-Ups simply means the chance of failure is reduced, while the Flame-Ups and speed-Ups allow you to cover more ground during the time you are invincible to the bomb blasts.

Hold R, move slightly, then stop. If you are still holding R, your character will walk in place.

The following items last only for one stage of battle. Pay attention to the upgrade's button selection.

A bomb upgrade that allows you to use B to detonate dropped bombs manually.
A bomb upgrade that allows the flame to penetrate more than one soft or destroy-able block.
A bomb upgrade that maximizes the first bomb instead of spreading out the power through each bomb.
A bomb upgrade that hides a dropped bomb as a little yellow dot until activated by enemy or yourself.

vDangerous Bombs:
A bomb upgrade that allows the first bomb to explode in a square radius.
A Bomberman upgrade allowing him to kick a bomb and stop it with X.
A Bomberman upgrade allowing him to blow away a bomb in your way with Y.
A bomb upgrade allowing for you to drop all the bombs you have at once using Y.
A Bomberman upgrade allowing him to pick up and throw dropped bombs.
A Bomberman upgrade allowing you to shield him from a bomb blast for several seconds.
A Bomberman upgrade allowing you to view the exit and all items in a stage.
A Bomberman upgrade allowing you to walk through soft blocks for certain amount of time.
A Bomberman upgrade allowing you to walk through bombs for a certain amount of time.

vInvincible:
A Bomberman upgrade allowing him to be resistant to all forms of attack including bomb and enemy that lasts only for a certain amount of time.
A Bomberman upgrade allowing him to be resistant to bomb blasts only.

Let Bomberman get out of one blunder such as a bomb blast or enemy contact.

Add a minute more to the time.

Another life. Cannot be stocked.

Decreases the number of bombs able to drop (but will not reach zero).
Decreases speed by one level (but will not reach zero).
Decreases firepower by one level (but will not reach zero).

Causes a state of illness or a black fog around your player that lasts for one minute. However, if you touch another player the illness will become their problem. Symptoms include speed minimization or lowest speed, will not be able to place a bomb, bombs will drop unexpectedly, and freezing.

A bomb that can bounce when punched or kicked.

Randomly picks a function of another item.