Free weapons:
Note: This procedure involves editing a game file;
create a backup copy of the file before proceeding.
Use a text editor to edit the "equipment.sss" file
in the "home" folder in the game folder.
Change the weapon costs to "0" to get them for free.

Hints:
Know what style of player you are when buying parts for
your gun. A more defensive-minded player might want a
longer barrel to take out enemies from afar, or a more
aggressive player might want a larger hopper to hold
more ammo. Hide, and hide often. On higher difficulty levels, the
computer will show no mercy in hunting you down and
taking you out. Find convenient places to crouch down
and hide temporarily until the other team has moved on...
then prepare to strike. Take notes as to where power-ups are located in each level;
they never go away, so you can go back if you're low on CO2
levels or ammo.