Level skip
Have Lara face north (the compass should become somewhat transparent), and enter the inventory screen. Select the load-game option and hold down the H, E, L, and P keys simultaneously. Close the inventory screen.

All items
Have Lara face north (the compass should become somewhat transparent), and enter the inventory screen. Select the small medkit, and hold down the G, U, N, and S keys simultaneously.

All weapons
Enable the "all items" code and continue facing north. Close the inventory screen, and re-enter it. Select the large medkit, and hold down the W, E, A, P, O, N, and S keys simultaneously