A Strider, (Half Life 2) is a tripodal robot that towers several meters above a human. Three essential parts to a strider's full operation is three legs, the hull, and the weapons system. The weapons system consists of two guns, a minigun style laser cannon, and a high powered plasma beam capable of reducing buildings to mere pieces of debris. In the Half-Life series, there are several ways to kill a strider. The most conventional way is to use a rocket launcher, (5 easy, 7 medium, 9 hard.) If a strider is dead, it lets out a mournful cry. In wilderness areas, striders are sometimes accompanied by Hunters. Smaller, tripodal equivalents of striders whose main ranged weapon is the ability to shoot electrically charged flachettes. Other ways to kill a strider are with the Magnusson Device, charged energy balls, and SMG grenades.
Tactics
Striders tend to follow specific patrol routes when tasked with defending a certain area, making them fairly easy to avoid, so long as shield scanners are not being used. When shield scanners do accompany a strider, they function as spotters for it, searching inside buildings and other places of concealment for targets the strider would otherwise be unable to see. Some traits are similar to the Guardian from Doom 3 after the Battle of the Nexus but that is the only time where they use this symbiont behavior with the shield scanners.
The RPG is by far the most efficient weapon for killing Striders, as its rockets do the most damage, though it takes more than 5 rockets just to kill one. Hand grenades, SMG grenades, and energy orbs do about half the damage of a rocket. Unlike Gunships, Striders tend to ignore all projectiles launched at them, focusing on attacking the player instead. To destroy a Strider during the Battle of White Forest, pick up a Magnusson Device with the Gravity Gun, launch it at the Strider's main body, and then set the Device off by hitting it with any gun. Do not attempt doing this until all nearby Hunters are destroyed, as they will fire upon a Device as soon as they see it.
Notes and References
Bibliography: http://half-life.wikia.com/wiki/Strider#Gallery