All Ammo and Items Code
Take out the pistols. Take one step back, then one step forward. Squat, and release the button. Turn around three full times. Then do a backflip.
Blow Lara Up
It is the "explosion" code. To see it, do either the skip level or all weapons cheat, but don't draw your pistols. Lara will die in an explosion that's unforunately a lot less cool than the one in TRII when Lara neglected to draw a flare.
Level Skip
Take out the pistols. Take one step back, then one step forward. Squat, then release the button. Turn around three full times then jump forward.