Press [F2] to open the console when playing then type:

Cheats - Results:
invincible (true or false/ 1 or 0) - God mode
health - Full Health
ammo - Full Ammo
invisible(true/false)- Invisible To Enemies
ghost - Fly / Walk Through Walls
walk - Turn Ghost Off 
stealth - View stealth amount


Item names
Use one of the following entries with the summon code. 

echeloningredient.ecamerajammer 
echeloningredient.echemflare 
echeloningredient.edisposablepick 
echeloningredient.ediversioncamera 
echeloningredient.ef2000 
echeloningredient.eflare 
echeloningredient.efraggrenade 
echeloningredient.elasermic 
echeloningredient.elockpick 
echeloningredient.emedkit 
echeloningredient.erappellingobject 
echeloningredient.eringairfoilround 
echeloningredient.esmokegrenade 
echeloningredient.estickycamera 
echeloningredient.estickyshocker 
echeloningredient.ethermalgoggle 
echeloningredient.ewallmine

Easy cheat mode
Use a text editor to edit the "splintercelluser.ini" file in the 
"\splinter cell\system\" folder. Scroll down until find any free keys. 
Bind the desired cheat codes to a key.


Demo cheats:
Type [TAB] to open console, type one of the following cheats and 
confirm with [ENTER]: 
 
Code - Result: 
health - Full Health 
invisible 1  - Invisibility 
ammo - Full Ammo 
fly - Fly Mode 
ghost - Walk Through Walls 
walk - Normal Mode 
playersonly - Freeze Enemies 
killpawns - Kill All Enemies
stealth - View stealth amount