Hold L2, then press X, R2, Triangle, R2, Square, L1.
If done correctly, you will hear the sound played when you get an artifact/relic.

This code will enable Lara to receive zero damage from enemies.
*Lara will still die if you jump from a high place*

Note: This code also lets Lara walk and swim on Eitr (the blue poison stuff) but you may not be able to get out of it. Re-rentering the code will deactivate it.

Hold L2 then press Triangle, X, Triangle, Square, L1, Circle.
If done correctly, you will hear the relic/artifact sound.
Reapeat code to deactivate.

This cheat allows Lara to kill enemies with one shot or melee attack.
*Does not work on Kraken*

**First, you must activate the "<a href="http://www.neoseeker.com/Games/cheats/PS3/tomb_raider_underworld.html#c81105" target="_blank" class="wikianchor">bulletproof Lara</a>" cheat.**

At the Great Hall in Lara's home (Prologue), before jumping down into the cutscene where Zip shoots at Lara, jump over the fallen flaming debris to your left. Then, climb the glass wall into the computer room and the cutscene where Alister is killed by the Doppleganger will start. A few cutscenes later, you will be in Southern Mexico and have skipped Mediterranean Sea, Coastal Thailand, and the Croft Manor levels.