Dragon Quest Heroes: Rocket Slime (DS)

Giggles in Tank Masters mode
Successfully complete the game. Then, talk to "Meggan", the green Egg Slime in the northwest building of the central part of town.

Gott Schliemen in Tank Masters mode
Defeat the final Boss and rescue all 100 Slimes. Then, defeat Hooly and the Shogun in the last round of Tank Masters mode to unlock Gott Schliemen in Tank Masters mode.

Knightro Slime tank in Challenge mode
Go inside the church and press Y, L(2), Y, R(2), Y, Up, Down, Select to unlock the Knightro tank in Challenge mode.

Schwarzen in Tank Masters mode
Defeat the final Boss. Then, go to where you defeated Slival on Mt. Krakatroda. Defeat Slival again to unlock Schwarzen in Tank Masters mode.

The Nemesis Slime in Challenge mode
Go inside the church and press Y, R(2), Up, L(2), L, Y, Down(3), Y, Select to unlock The Nemesis tank in Challenge mode.

Female slime tank
Go inside the church and press Y, R(2), Up, L(2), L, Y, Down(3), Y, Select to unlock the female slime tank in Challenge mode.

Helmet slime tank
Go inside the church and press Y, L(2), Y, R(2), Y, Up, Down, Select to unlock the helmet slime tank in Challenge mode.