Strider

From Halflife2.net Wiki

Striders are Synths that looks like towering, three-legged spiders. They are very resilient and well-armoured, meaning that they can only be damaged by explosions. Striders are mainly used by the Combine to patrol the streets of City 17. However, once The Resistance starts fighting the striders are sent out to clear the strees instead.

Striders have three ways to attack. The first is their pulse cannon, a rapid-firing weapon with significant firepower and the one the striders use the most. The second is a disintingration blast, a fearsome weapon capable of destroying many obstacles and any human unfortunate enough to be caught in its blast is destroyed utterly. The third way is simply to impale their victims on their long legs. Due to their powerful weapons and the amount of damage they can take, Striders are some of the most dangerous enemies in Half-Life 2.

Striders can be seen early in Half-Life 2, patrolling streets. Players do not get to fight them until much later in the game, however. Striders also appear in Episode One.

It is now clear that with the introduction of Episode 2, Striders will now have smaller relatives known as Combine Hunters.