Make sure Lara is facing EXACTLY North
Go to the INVENTORY Screen [ESC]
The needle on Compass should be transparent - if not, you are NOT facing exactly North.
Go to Large Medi-Pack
Press and hold W, E, A, P, O, N, S for a moment, then release
You should now have all Weapons
Chambers Of Tulun: Avoiding damage
In big room in the Chambers Of Tulun where the man that makes shockwaves chases you, wait for a gold beetle to appear then start running around. The beetle will grab you and you will hover around. If you move too much, hit a wall, or get hit by that man, the beetle will let go, slice up your neck, and you will take damage.
Depth charge launcher
If you have the grenade gun, it can also double as a depth charge launcher. Point at a pool of water and fire. The grenade will sink slightly and explode. Normal ammunition sinks slightly deeper.
Diving death
Go to a ledge with a long drop and do the special dive. Lara will land on her head and die.
Easy rolling
To roll easily, instead of pressing [End] press the [Up] + [Down].
Easy way to face exactly north
Find any block that faces north. Climb up or jump to it. Go to the inventory screen and your compass should be transparent to confirm she is facing exactly north. This may also be done by climbing a block that faces south. Press Roll once to point exactly north.
Hint
Here is an easy way to make sure Lara is facing EXACTLY North...
Find any block that faces North
Vault on to it
Go into INVENTORY
The Compass Needle should now be transparent!
Important objects from current level
Have Lara face exactly north. Enter the inventory screen and look at the compass. If it is not transparent, try positioning her again. Go to the small medipak, hold B + I + T + S, then release those keys. Important objects, such as keys, for the current level will now be available.
Killing knights
To kill the knights found in The Lost Library, shoot the blue gem in their chest. Do not attack from the back, as it is just a waste of ammunitions. Six or seven direct hits with the shotgun or the crossbow will kill them.
Killing the red ninjas
Shoot at them. When they start spinning their blades, put up your gun, bring it out, and start shooting. When your gun is put up, the ninja will begin to stop spinning his blade and will not start spinning for a few moments. This gives you enough time to blast him.
Level Skip
Make sure Lara is facing EXACTLY North
Go to the INVENTORY Screen [ESC]
The needle on Compass should be transparent - if not, you are NOT facing exactly North.
Go to Load Game
Press and hold H, E, L, P for a moment, then release
Close the Inventory Screen [ESC] - You skip to the next level!
No damage from Horus
Step into the blue light Horus was standing in before you put the armor on him. He can keep attacking, but it will not get through the light. Do not get behind it. If you do, his weapons will still hurt you. You must be inside the blue light. This works best when the "All weapons" code is enabled.
Save explosive ammunition
Save explosive ammunition (grenade launcher, Cross Bolt, etc.) for tougher opponents when fighting the skeletons by using the shot gun against them. Get the skeleton between you and a ledge and blast it. The skeleton will fall off the ledge and cease the exist. Since shot gun ammo is more prevalent in the game than the explosive ammunition, this will allow you to save it times when there are no ledges to help.
Save health packs
You can save health packs by going to a different level, then coming back for health because the levels are so numerous and close together.
Training level gold skulls
The first skull is at the beginning toward the left.
The second skull found is in the shallow water below the very first jump you are instructed to do.
The third is below the running jump section of training.
The fourth one found is in the water of your swim training session.
The fifth one found is at the crawl space where you obtain the pack.
Turning on all the switches in the Star Room in the Lost Library
First, start at the switch across from the reset pad. Face the reset pad and number each switch starting with the one you are at as "1" and then going left, 2, 3, 4, up to 7. Then, activate the switches in the following order: 1, 3, 2, 7, 5, 4, 6.
Underneath the Sphinx: Getting out
You can sneak past the bulls without waking them or worrying about locking them in their cages. First, make Lara face north and enable the "Unlimited items" code: Open the inventory screen and you should have all four keys you are supposed to collect in the level. Go to the far right and walk slowly past the cage and the pillar. Then, sidestep to the right until you are almost in the right corridor. Then, go behind the bulls and enter the stone tablets: right, left, middle. Sneak to the left and go to the gate you opened. From there, cross the two pits and place the keys in their correct locations. Go through the gate you opened and head across the monkey swing. Grab the scriptures and exit the level by the monkey swing. Remember to walk across the empty room after the scripture room, as there are spike traps located there.
Unlimited Ammo / Gear
Make sure Lara is facing EXACTLY North
Go to the INVENTORY Screen [ESC]
The needle on Compass should be transparent - if not, you are NOT facing exactly North.
Go to Small Medi-Pack
Press and hold G, U, N, S for a moment, then release
You should have everything Unlimited now