Hunter

Characteristics

 The Combine's Hunter is a type of Combine Synth meaning it was once an organic creature of its own race and world of origin but have been enslaved by the Combine and have both evolved and been modified to fulfill a role in the Combine military.  The Hunter takes on similar features to its larger counterpart, the Strider (hence the nickname), such as its three legs (two on its side, one on its back) and helmet-shaped head, which is covered in metallic-blue medium armor. Its reverberating growls and groans and clanky leg sounds also strike a resemblance to the Strider. However, behavioral-wise is very different.  The Hunter is stout in comparison but also much faster and more agile being able to quickly dodge out of danger's way and maneuver through tight spaces including doorways. It has two eyes aligned vertically, which can move independently in any direction, scanning both its surroundings above and below simultaneously, giving it an advantage in tracking and detecting enemy movement. These eyes, which appear to be cybernetic, most likely enhance its sensory perception, which would be what would make it so skillful at locating its targets. Below that are two guns for its primary attack and below those are two small arms with blades on the end
 

Attacks & Abilities

- The Hunter's most basic attack is an explosive flechette, which it fires rapidly out of two guns placed at the base of its head. In addition to causing damaging from a direct hit, once the flechettes latch on to any object they detonate shortly after. 
- Any light-medium weight items scattered around the environment the Hunter can punt out of its way or break through them. These include doors and large breakable obstructions.   
- The Hunter also has a charging attack, where it can't turn much once started but is very powerful and will knock its target backwards. 
        

Tactics

- The Hunter's armor withstands most gunfire fairly well with the exception the AR-2 and is more susceptible to explosive damage, but what is usually more effective is blunt trauma, by means of firing objects at it with the Gravity Gun. Running them over with the car at a high enough velocity works as well.
- To counter the hunter's ranged attack and make it back fire on itself, the player can make the hunter fire the flechettes into an object the player holds up with the Gravity Gun and fire that object back at the hunter as the flechettes are about to explode for maximum damage. For killing a Hunter this exact way unlocks the achievement "Payback". 
- Undisputedly the best way to take out a Hunter is with the AR-2's secondary fire, which will kill it with one hit.  

Appearances

 While the Hunter's role was most prevalent in Half-Life 2: Episode Two, it makes appearances in both the first and second episode. 
 
EPISODE ONE: 
In the footage from the data packet sent by Dr. Mossman that Alyx recovers from The Citadel, the Combine are seen breaking into the base she is hiding in when the camera spins around and falls revealing a brief glimpse of the Hunter following a few Combine soldiers. 
 
EPISODE 2: 

The first time they appear is after you reconnect with Dr. Kleiner, Eli Vance, and Dr. Magnusson at White Forest base and try to open up a gate to a mine shaft, where the Hunter reveals itself twice (very briefly) before making its biggest impact where it sneaks up behind Alyx and punctures her in the abdomen twice with its two arm blades and then leaves after she falls unconscious. 
Right after a puzzle that entails getting power back to a radio transmitter, a Hunter attack ensues, this one being the second encounter but the first time the player fights against them. 
After investigating an Advisor Pod a battle begins outside with Hunters in the fray. 
Towards the end of the driving portion of the game, there is a battle with the player holed up in a large house, where Hunters lurk around. 
White Forest falls victim to random power shortages, which the player is sent to investigate. The player discovers that the cause was a Combine assault with Hunters. 
In the climactic battle defending White Forest from an onslaught of Striders, groups of Hunters eventually join in the battle as the Striders' escorts.