X-Com: UFO Defense Cheats

Level skip:
Press [Ctrl] + C or [Ctrl] + G while in the battlescape screen to complete the current level with the results of the previous level.

Extra money:
Begin your new game and build a base. Save it, and exit the game. Open the game folder and you should see folders named "GAME_1" to "GAME_10". These are the saved game folders. Enter the saved game folder that corresponds to the game that you saved. The order of the saves is the same as in the game ("GAME_1" is at top, etc.) After you open the folder with your save, make a back up of the "LIGLOB.DAT" file. Then, open the original "LIGLOB.DAT" file with a text editor. You will see some encrypted data. Press [Enter] so that text jumps to line two and line one is clean. Now submit FF FF 7f in the line one over the encrypted data and save the file. Then, start the game, load your saved game, and enter your base. You should now have $1,713,399,398.

Free manufacturing:
Pick the item to be manufactured, but assign no engineers and leave the number to produce at zero. Now assign as many engineers as desired but only manufacture one item. Use tanks with this trick to easily make money.