Tomb of the Lost Adventurer and Hidden Room / Tomb Raider 2013 HD

The dlc called Tomb of the Lost Adventurer is a great one not just because of the nice treasure you get but also because of the loot hidden in a cave. This one is almost easy to miss or forget even if you own the dlc. Since this tomb you come across in the beginning of the game it is almost easy and certain to forget that you must return once you have the grenade launcher which you acquire way later in the game to blast the wall to get into the secret room. Once inside you find a room full of crates, ammo and lock boxes all to which can come in handy when you need the things to upgrade your weapon before the final battle with the Oni.