All Items Cheat

There is a code for All Items as well - turn Lara directly North according to her compass - enter the inventory screen and highlight "Large Medipack". Hold L1 & L2 & R1 & R2 & Down and press Triangle. (A good way to have Lara face exactly North is to have her hang from a ledge that is facing North. While hanging from the ledge press Select to enter the inventory screen.
Submitted by Hatshpset

skip levels

Face north go to inventory screen and hold l1,l2,r1,r2,Triangle and up.

or Step by step
1.make sure lara is facing directly north according to her compass.
2.pull up your inventory screen and highlight LOAD
3.press and hold all four shoulder buttons and up at the same time.
4.press triangle and you will skip the level.
Submitted by sue.jeffery & Noesche Abner & Elizabeth Horne

all weapons cheat

same as above except you go to the small medi pack press up on the control pad and triangle
Submitted by Noesche Abner

unlimited medipaks

same as above except you go to the large medipak an press down on the control pad and press triangle