Though they are bad for Snake's health, he insists on bringing them along with him on every mission. In fact, at the start of the game, these are all he has on him. They serve a small purpose, but you'll have to make it to the end of the game before they are of any use to you.
In order for Snake to infiltrate deeper into the enemy base, he'll need to get his hands on eight separate access cards. Most doors in the game will only open provided Snake is holding the appropriate card. You must actively try every card in your inventory to find the correct card.
Binoculars
Gas Mask
The binoculars are an item that Snake finds very early in the game. They permit Snake to get a sneak peek at what may lie on the other side of the current screen you are on. Activate the binoculars, and push in any one of the four directions to take a look at the neighboring screen.
Certain locations in the enemy base are filled with a toxic gas that causes Snake to slowly lose health if he breathes it in. The only defense against losing health is to don a gas mask.
Rations
Cardboard Box
As Snake takes damage throughout the game, his health meter will shrink, and he will die if it ever empties. In order to prevent this from happening, Snake can eat a package of rations and completely refill his health meter, up to the maximum that his current class allows.
Part of Snakes mission is to evade capture and attract as little attention to himself as possible. In addition to the guards that are stationed throughout the base, there are cameras mounted on rails. They will trip an alarm when they detect intruders. However, they are not programmed to react when they see ordinary objects, such as a box…
Transmitter
Enemy Uniform
If Snake is captured, the enemy will find a way to track him in the event that he manages to escape. As long as this transmitter is on him, the enemy will be able to react to his presence even before spotting him. If you happen to notice this in Snake's inventory, use it to get rid of it immediately.
At one point in the game, rumors of Snake's presence will be running rampant throughout Outer Heaven. He'll need to get past a set of guards stationed in front of a building, but with everyone on high alert, he'll need a good disguise to get past them.
Bomb Blast Suit
Infrared Goggles
A bomb blast suit is very heavy, and made to help its wearer withstand any force that might attempt to blow him away. If ever Snake finds himself in a situation where an invisible force makes it difficult to proceed, a bomb blast suit may be just what he needs to push his way through.
Though utilized only a few times throughout Outer Heaven, infrared laser beams prove to be an effective security measure. IR laser beams detect intrusion and sound an alarm when a beam is broken. Though invisible to the naked eye, these beams can be seen by someone who wears infrared goggles.
Mine Detector
Iron Glove
A few outdoor locations have been laced with land mines for extra security around the buildings. If Snake would like to make it through these sections unharmed, he better have a Mine Detector handy to help him avoid the danger.
As long as the iron gloves are in your inventory, you'll be able to break holes in weak sections of certain walls. Punching a wall where there's a weak spot will also make a sound different than the normal one.
Antenna
Body Armor
Once Snake enters the second building, he will find that his communications with his team are cut off. The enemy has effectively jammed his communications, and he'll need to find a special antenna to boost the power of his transceiver to send and receive communication signals.
The body armor is not a necessary item for the completion of the game but it sure does help. When worn, it will cut the damage that Snake takes from bullet wounds in half. It must be activated to be effective.
Antidote
Compass
Throughout Snake's adventure, not all of the enemies that he faces will be human. Some will be animal, and among those, some like the scorpion will be poisonous. If Snake ever becomes infected by the venomous sting of a scorpion, only this Antidote will prevent him from slowly losing health until he dies.
A desert separates two of the buildings. In order for Snake to navigate his way through the desert to the other building, he'll need to find a Compass which can keep him heading in the right direction. Otherwise, he'll wander aimlessly through the desert.
Oxygen Tank
Flashlight
At certain times in his mission, Snake must submerge himself in order to further infiltrate Outer Heaven. However, without oxygen, he will slowly lose health while he's underwater. Possession of the oxygen tank will help him safely swim through the water unharmed.
Some underground sections of Outer Heaven lack electricity. You'll need some way to pierce the darkness in order to traverse through the darkness that you encounter. Activate the flashlight to get a better view of the area around you.
The handgun will be Snake's primary weapon throughout a good portion of the game. It is simple to use, and ammo for it is in pretty good supply. It fires straight, and bullets travel all the way across the screen.
Before you find the silencer, a single shot from the gun will alert any nearby enemy soldiers to your presence. With the silencer attached, Snake becomes a far more stealthy assassin, capable of taking out a target without anyone else nearby noticing.
Plastic Explosive
Land Mine
You won't have much use for plastic explosives throughout the game. They may also be used as a weapon, but Snake will have to find an enemy they are effective against. They will be of critical importance at the end of the game.
While the enemy tries to get the best of intruders by scattering land mines around the ground, Snake can turn the table on the enemy and place his own mines on the ground for the enemy to trip. They are particularly useful against objects with heavy armor.
Remote Guided Missile
Grenade Launcher
Remote guided missiles allow the shooter to launch a missile, and control it as it flies through the screen, in an effort to hit a distant target that is not straight ahead. Controlling the missile takes concentration, so shooters cannot move while the missile is actively flying.
There are some enemies where an ordinary bullet simply won't do. In these situations, you need something with a little more punch, like a grenade. The grenade launcher will fire grenades a few feet ahead of the shooter. A set of cross-hairs will be visible to give you an indication of where the grenade will hit.
Sub-machine Gun
Rocket Launcher
The sub-machine gun fires its own round of bullets. They fire fast and spray a bit back and forth while being shot. The machine gun is good for enemies that you need to try to hit at a slight angle.
The ultimate in destructive power, the rocket launcher fires off a rocket that blasts its target with tremendous force. Very little can withstand the power of these rockets, but some enemies are equipped with anti-rocket armor, so don't expect it to work on everything.
