This is was originally made by some one else but I added the Max ammo, Max Health, Noclip mode.
Dpad Up turns you invisible
Dpad Down gives you Invicibility
Right Thumble gives you NoClip Mode
Left Thumble gives you Max Ammo and Max Health
Back Button turns off Invisibilty and NoClip Mode
Might have to press the Dpad Down after each save to turn Invicibility back on.
If I can find more cheats I will update in future.
Make a backup of your ThirdEchelonUser.ini then either ftp this to your hdd if you have splinter cell on your hdd, other wise put this file in your splinter cell back up before you burn it to disk.
Have fun!