God Mode
Open the config.cfg file (located in your installation folder) with Notepad and change the following line:
cfg_SPPlayerDamageModifier = 0.35

-to-

cfg_SPPlayerDamageModifier = 0.00

This will cause any ships under your command to take no damage in Campaign mode.

NOTE: Always make a backup before modifying game files. There are several other settings within this file that you can play around with for additional cheats. Be sure to write down the original value or backup the file before changing anything else in case it causes problems in the game.

Unlock All Missions
Find "art_cfg.h" file in the game directory. Change the "0" in the "GIVE_ALL_MISSIONS" line to "1".

Better Transporters
In certain cases you might need to toggle off the READ ONLY attribute first. Using your text editor alter the "rts_cfg.h" file in the game directory. Change the value in the "TRANSPORTER_MAX = 5" line to a higher number to transport more people.

Faster Transporters:
In certain cases you might need to toggle off the READ ONLY attribute first. Using your text editor alter the "rts_cfg.h" file in the game directory. Change the value in the "float TRANSPORTER_DELAY" entry to "0.0" (or "0.1").

Better Sensor Arrays:
In certain cases you might need to toggle off the READ ONLY attribute first. Using your text editor alter the "rangeScan =" to "32000.0f".

Start with More Cash
In the config.cfg file, apply the following change:

// Starting balance
cfg_InitialCommandPoints = 9999999