500 credits
Pause the Game and press Right, Left, Right, Left, L, R, Up, Up, R, R, L, L. Can only be used 1 time per game.

1000 credits
Pause the Game and press Up, Down, Up, Down, Left, Right, L, R, L, R, R, L. Can only be used 1 time per game.

5000 credits
Pause the Game and press Up, Right, Down, Left, L, L, Right, Left, R, R, L, L. Can only be used 1 time per game.

1000 bucks
Pause the Game and press Up, Down, Up, Down, Left, Right, L, R, L, R, R, L.. Can only be used 1 time per game.

Blast ammo on the wall
Try to find the richochet gun on the 2nd mission. Find a wall and blast the ammo on the wall. Follow the ammo to the next wall and try to dodge it and so on.

Simple Serris
The easiest way to beat Serris is to go to the very right of the room, go to the top of the ladder and shoot fro there. That way Serris can't touch you, and you have an easy way to shoot him.

Castle 3 Multiplayer Map
Beat the Abominable Snow Turtle(Mission 3)

Single Pak 3 Multiplayer Map
Beat the King of the Chameleon(Mission 1)

Single Pak 4 Multiplayer Map
Beat Saurian General(Mission 2)

Wasteland 1 Multiplayer Map
Beat the Giant Mech Turtle(Mission 4)

Wasteland 2 Multiplayer Map
Beat Dark "Devan" Shell(Mission 5)