At the main menu hold down the right shift button and press F3,F4,F3,F3,F4 Then press F1 to bring up the cheat menu
10/25/2005
Get Rocketlauncher in the first level
Before you go through the monkey head, look to your right. There should be a small waterfall.A little bit more right, there is a platform up on the wall. Shoot at the piece of wood under this, and a rocketlauncher will fall down.
11/29/2005
Difficulty Bonus
Start a new game under the difficulty of your choice. At any time, go back to the main menu, select Custom Level, and play it through in Serious Difficulty. Load the game you had previously started, and although the starting difficulty will have stayed the same, at the end of each level you will get the difficulty bonus for Serious difficulty.
5/20/2006
Enable Developer Cheats
Hit the tilde key while playing the game to bring up the console and type "sam_iEnableCheats=2" without quotes. Then pause the game and hit F1 and you will have enabled the developer cheats rather than the regular ones.
Sam will take no damage and will not be knocked back.
God Mode Option
Sam's Enemies will no longer see him
Invisibility Option
Destroy all enemies simultaneously
Kill All Option
Bring Health to 200%
Refresh Heath Option
Turns the Heads Up Display On/Off
Toggle Hud Option
Makes Sam Incredibly fast and Jump Far
Turbo Option
Unlocks all levels in the Custom Level Menu
Unlock Levels Option
6/7/2006
Level Skip
After you do the F3, F4, F3, F3, F4 cheat at the main menu, when you are in a level, you can press F2 (NOT IN THE CHEAT MENU) to skip to the next level. This works in any level but the last one.