Items from boxes
Press Square to break boxes then press Triangle to pick up the item. Note: Note all boxes contain items.

Avoid Damage From Falling
When you're falling, enter Combat Mode right before you hit and you'll incur no damage.

Pistol whip
Press Square to pistol whip your adversary. Note: This works for all guns, not just the pistols.

Drink from canteen
To drink from the canteen, hold X. If you instead tap X, it will take longer. Holding X also helps when you fill your canteen.

Magical barrier
Equip the PaCheng and press R1 to block.

Art gallery
Collect all artifacts in the game to unlock an art gallery.

Secret area
On the first level when you first encounter crocodiles, kill all of them with your machete. Then, swim to the left next to the entrance to the temple.

Swim behind the waterfall to pull up on a small ledge. You will not be able to see much, there is a box here. Break it open to get a bundle of dynamite.

Break wall in Istanbul Sunken City
When you reach Istanbul Sunken City, to break the damaged wall, hover above the head in the water with the crane.

Press X and it will automatically break it up.