Extreme Assault

At the main menu type "levelx ", and don't forget to leave a space after the "x", to enable the cheat codes.
Then press in the game : 
alt+1:full ammo
alt+2:weapon upgrade
alt+3:energy up...
alt+4:god mode
alt+5:?
alt+6 : end mission
alt+7:deactivate enemies
alt+8:change to heli mode
alt+9:change to tank mode
alt+0: find out by yourself