Shielder

Shielders  are a type of zombies introduced in. It appears similar to a Stalker, except it carries a riot shield in front of it, which becomes overgrown with infection between each evolution of the Shielder. The shield blocks any and all bullets from the front, rendering the Shielder nearly impossible to kill from the front. The Shielder, however, does not have such armor on its flanks and it turns slowly versus other zombies, rendering it easiest to go from the sides. When shot directly, however, the Shielder has a small amount of physical resistance, which gradually increases as the Shielder evolves.

Tactics
Despite appearing near impenetrable at first, the Shielder can be easily taken down with the correct methods. A few are as follows:
 * Flank and attack from the sides or rear. Shielders, despite its slow turning speed, has more health than a Stalker of the same type, yet will still go down easily when its weakness is exploited. This method will use the least ammunition, but it is problematic to set up at times, especially if the Shielders are in a group, if the Shielder is confronted in a narrow corridor, or if the Shielder has many problematic modifiers, such as Regenerating.
 * Moving to the side of the Shielder may cause it to attack you while you're moving, so you can also shoot at the Shielder while you're maneuvering around it to keep it from doing so.
 * Weapons that deal damage over time will still affect the Shielder, and shooting a Gigavolt or Trailblazer will arc around to hit the Shielder regardless of direction.
 * Weapons that deal area of affect damage, like the Gebirgskanone, will bypass the shield entirely and damage the Shielder like it would normally. Rocket Launchers with an even greater blast radius, such as the HVM MPG or the T-101 Feldhaubitz, will instantly damage large groups of Shielders you may face. Also, using M45, M48 UHE Fragmentation Grenade works very efficiently as well, and is advised to use these spares only for this zombie.
 * Since the Shielder's physical damage resistance will still reduce the damage from the area-of-effect damage, using non-physical explosion weapons will bypass that unless if the Shielder in question has other resisting modifiers. Currently, there are eight non-physical explosion weapons: The T-102 Jagdfaust, the HIKS 3100, the Luftplatzen, the Vitriol, the CM X-1 Furie, the HIKS S4000, the Zerfallen, and the Torment.
 * Lastly, the Assault Class's Close Quarters Combat Skill. Using it directly in front of the Shielder at point-blank range will damage it as if the shield was not there, eliminating the need to flank or maneuver. When dealing with stronger Shielders (Evolved and up), doing any of the other strategies is advised, as it will take multiple uses of the skill to kill stronger Shielders, which will quickly drain the player's energy and increase the risk of taking high damage. The knife does provide some stopping power, however, which partially mitigates this.

Trivia

 * Prior to the update on December 10, 2014, the Shielder's shield did not block every bullet. Constantly shooting it from the front would eventually bypass the shield, damaging the Shielder. After the update, however, the Shielder's shield became fully impenetrable, and only rocket launchers can shoot through the shield. But with the newest update, they have fixed that and now Shielder's shields do not block every bullet/rocket again.
 * Although the Shielder's description said "Known only as Shielders", they can also be called zombified police, as the description also said "These zombies were like Stalkers who used to be law enforcement". In the event Shielder Bounty, the Shielder is seen holding a shield with the blurred word POLICE on the shield, therefore concluding that Shielders are zombified policemen, possibly riot anti-mob forces.
 * The more Shielders mutate from Regular to Apex variants, the more pasasite-like tendrils appear & wrap around their right arms & shields. This is likely the mutation that the virus provide the host body/infected, thus making them & their shields much more reinforced.