Tom Clancy's Rainbow Six 3 cheats and cheat codes for Playstation 2

Unlock stage select and difficulty modes:
On the main menu, press START to access the Campaing, Custom Mission, Split 
Screen, etc. options. Press L1, R2, L2, R1, LEFT, RIGHT, SQUARE, CIRCLE. 

Unlimited Ammunition:
If you have out of ammo for M60s, pistols, or assault rifles 
press Circle to reload.  Look at your clip counter. It might say 21, 
for example, and in bold numbers next to it 13. That means that you are 
expending your 13th round on your 21st clip. If you press O, you will 
reload to your maximum number, but still stay on your 21st clip.
Repeat as many times you want.