Cheat mode:

Find the outcast.ini file in your main Outcast directory. Use any text editor to change the following values in the outcast.ini file (note - make a backup of the file before making any changes):

More money and health
Change:                 To:
MoneyChest=5.0000000    MoneyChest=5000000.0
Money=1.0000000         Money=1000000.0
Life=5.0000000          Life=5000000.0

Invincibility
Change:                      To:
(Human)
HeroDamageScale=1.000000000  HeroDamageScale=0.000000000 

Ammo boxes have 999 bullets
(SimpleGun)
AmmoBox=999.000000 

Thanks to Revolution readers Ed@ie, Raptor, Ivan, and Dino Dusanic!