I saw this link over on the Far Cry forums. Someone apparently made a hacked config file. I tried it and it seems to work ok for me. Just hit ESC to bring up the menu after putting this file in and you'll have options for:
9999999 Health
9999999 Armor
All Weapons
Some of the weapons are invisible on my system, but for the most part, it seems to work. I only tried it once though.