Half Life 2 - Enemies Guide
A guide by Will
This is a very large guide and so the easiest way to find the enemy you want is with the contents below. This guide is also applicable for the Xbox 360 version of the game. If you spot that I have forgotten an enemy then please do email me.
Scanners
Scanners are one of the first enemies you will see in Half Life 2. Put simply they are floating security cameras, they fly around City 17 and observe the citizens. If it gets in your face it will blind you with a bright, white flash. While this won't hurt you it can get irritating after the fourth or fifth time. The easiest way to take these down is from a few hits with the crowbar or a few pistol shots.Combine Metro Police
These are the first people you see when you get off the train in City 17. When you first see them they are carrying what appears to be a truncheon and will hit you with it if you do something that isn't allowed. When you start to escape they will attack with pistols and SMG's. The best way to combat these troops is to aim for the head, that way it will take less shots.Manhack
The first time these appear is in Route Kanal. They are basically, flying blades of death. However, they are incredibly easy to kill. The best way to attack them is to hit them with the crowbar as they fly towards you. If you come up against these then it's fairly likely that there will be Combine Soldiers nearby. If you have the Gravity Gun then you can grab one with that and use it as a weapon against other enemies, or simply fire it against the wall to destroy it.Headcrab
These parasitic.. parasites are first seen in large numbers in Ravenholm.
The fly towards your face with the intension of turning you into a zombie. They are quite possibly one the scariest enemies in Half Life 2 (especially playing on a laptop late at night), but are easily countered. As they jump at you a simple blow with the crowbar will be more than enough to kill them. Later in the the game, they can be killed with objects you fire from the gravity gun. Barnacle
You first see Barnacles in the level Route Kanal. Put simply they are large blobs of goo that stick to ceilings and wait for other living things to walk underneath. Their long tongues stick to you and slowly drag you towards their mouth. If you do become ensnared, then the easiest way to kill them is to fire a few shots at them or give them a smack with the crowbar. If you spot one you can throw an inanimate object at them to distract them for a bit. For large groups of barnacles then you can put a flaming barrel underneath them and it should kill them all easily.
There are a few good uses for barnacles:
- They will kill other enemies if you guide them towards barnacle traps.
- Their tongues also make handy makeshift lifts to get to higher places.
Zombie
Zombies are just humans that have been attacked by headcrabs and have become walking corpses. You should be careful with these as killing the body will only leave the headcrab to fall down and look for a new host. When you do encounter them aim for the head as that will kill both the zombie and the headcrab. The best weapon to use against them is the shotgun as this is most likely to kill them in one shot.
Poison Headcrabs
These pests first appear in Ravenholm, while they resemble normal headcrabs 
their cry is slightly different and you should take far more caution to fighting these. They move a lot faster than regular headcrabs and if you are bitten then your health will drop all the way down to one and a single hit from anything will kill you. 
After a while the HEV will provide and antidote and you health will slowly rise back to what it was before. The most likely way to see thee headcrabs are grouped together on a poison zombie. Throw a grenade at them or hit them multiple times with the shotgun to kill them before they get a chance to attack you.
Fast Zombies
These are very much like normal zombies, except they are a lot faster and are more likely to kill you. They crawl about on all fours and are much more skeletal than regular zombies. Their jump attack is very precise and difficult to avoid. The Fast Zombies can also scale buildings and are likely to pop up from hidden corners. The best way to take them down is to fire the shotgun when they are very close to you.
Combine Soldier and Prison Guards
These troops are far more intelligent and also better armed than the Combine
officers first seen in City 17. They wield the shotguns, SMG's., Pulse Rifles, and even grenades. These enemies also have a melee attack that they use against you. Advanced combat tactics are needed to deal with groups of soldiers. As usual, aim for the head, especially with the pulse rifle. A well placed grenade can be used to take down groups of soldiers. The Gravity Gun can be used to pile up barricades or launch heavy objects at the Combine Soldiers. Antlion
Antlions are large, insect like creatures that like in the sand. They will only appear if you step on sand during the level they are in. These enemies are very 
quick and are capable of flying large distances. During Highway 17 you may see large pillars on the beach, these are thumpers and if they are activated Antlions will not go anywhere near the immediate area. The easiest way to kill one is with a shotgun blast, however; it is pointless trying to kill them all as they continue to spawn while you are standing on sand.
Before you begin the assault on Nova Prospekt you gain a pherapod which ultimately stops them attacking you and "turns them on your side".
Antlion Guard
Antlion Guards are basically larger versions of the antlion. This huge creature will attack you with a charging head butt. To take this down it is likely that you will need to use the more powerful weapons, such as the secondary fire of the SMG or the Plasma Rifle.
Roller Mine
These small, ball like machines are found around Highway 17. They stick in the ground and will activate when they sense movement. If they activate they roll towards you and inflict electrical damage. The mines will also attach to the side of the buggy and inflict damage on that, this will push it violently off course. The easiest way to deal with them is to suck them up with the Gravity Gun, and blast them into the ocean.
Combine Elite
These are the toughest version of the Combine troops. They have a pristine white suit which allows them to take far more damage that police or soldiers will. They use Pulse Rifles and will also attack with the plasma orb. While the orb is damaging, it also knocks you back a short distance, and so could knock you off the edge of a platform. The best way to take them down is to use the secondary fire of the Plasma Rifle, or a close shotgun blast.
APC
These large vehicles are used by the Combine to transport troops. It has a powerful mounted machine gun on the front, and also fires rockets which home in on you. The first time you have to take one of these down you are equipped with a an air boat with an unlimited supply of ammunition, so you shouldn't have to worry how to take one down.
Automatic Turrets
Auto turrets are gun turrets that are mounted on tripods. They detect movement and will fire at you if they detect it. Their fire is incredibly deadly and you will die from a few shots. If you find yourself trapped in a corridor with them, then grab a large item with the Gravity Gun and you can use it as a shield. You should try and knock them over as soon as you can by throwing a large object at them with the Gravity Gun, or throwing a grenade at them.
When you are in Nova Prospekt Alyx will reprogram them so that you can use the turrets to attack the Combine. You can carry one around with the Gravity Gun and use it as a machine gun with infinite ammo.
Ground Turrets
These are very similar to Automatic Turrets as they are motion activated and will kill you fairly easily. They don't appear until almost the last level of the game, so the easiest way to kill them is with a grenade. 
They pop out of vent like areas on the ground and so a well tossed grenade inside the hole will knock them out easily.
Gunship
The Combine gunships are one of the most fearsome enemies in the game. They hover around like some sort of annoying pest and the only way to take one down is with RPG's There is a mounted machine gun on the nose of the ship, these will fire at you and will also down RPG's that are flying towards them. The trick is to fire away from the ship, and guide the RPG in from the side with the laser site. On normal difficultly it takes 5 direct hits from the RPG to take one down. If a gunship ever appears and you do not have any RPG ammo, then you should either hide or run away.
Strider
The Strider is by far the hardest enemy in the game to take down. Each of it's enormous legs are razor sharp and will kill you if it lands on you. The machine gun on its nose is also a fearsome thing. By far its most deadly attack is the giant white laser that will kill you very, very quickly.
The best way to bring down a Strider is with RPG's, much like the gunship. However, you can also use the secondary fire of both the SMG, and the Pulse Rifle.
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