This method involves editing game files, backup before doing so.
In the root directory of the game you will find a folder called "Packs", in here you will find a zip file called "Pak0.zip". Open this with winrar (or any other program that reads zip files). In here you will find all the files you need to edit. Here are some edits that i found quite usefull:
Make vehicles (almost) invincible:
<item name="machinegun1" price="2000" />
Weapons ammo and damage:
<damage value="800" />
To change the clip size edit the following line:
December 16, 2009 - 1:28pm