World War II Zombies uses a system of Special Abilities with Mods used to buff specialists or the player overall. Specialists are four abilities that affect the players and zombies in beneficial ways. Players are locked to one ability per match. Mods are secondary abilities that buff players directly. Players can use Mods to add behaviors to their Specialists, and they can buff themselves with general improvements. Mods are limited to three on each player. 

Special Meter

The Special Meter is charged by earning points. Each use of your Specialist increases the points needed by a linear amount. The hard cap for charging this meter is [known?], but the upper limit can reach fairly high counts.

There is little to no way of manipulating the Special Meter, aside from a Mod and a reward from The Frozen Dawn's major Easter Egg. When completed, all players in that match are granted passive Special Meter regeneration, charging the meter fully within two minutes (and it can go into overcharging the meter). Refer to Specialist Training for more information.

Camouflage

"The player is ignored by zombies. Shooting firearms shortens the special ability's duration."

Camouflage is a Specialist ability concealing the player from zombie's targeting for a 20 second duration. Shooting while the ability is active drastically lowers your time. Shooting and activating this ability can be dangerous; the ability trigger is quick, so use this ability in a timely manner.

Exfiltration

"Allies revived while using Camouflage are also hidden temporarily."

Field Medic

"Revive fallen teammates quicker while using Camouflage."

Mobilization

"Increased movement speed while using Camouflage."

Players move 1.5 times faster while in Camouflage.

Saboteur

"Lethal equipment does significantly more damage while using Camouflage."

Serrated Edge

"Melee attacks deal extra damage over time while using Camouflage."

Hitting a zombie while in Camouflage marks them for damage over time, gradually increasing. The damage is very unnoticable, oddly lasting X seconds for small values of damage. The player does earn 5 Jolts for meleeing a zombie while active.

Survivalist

"Gain 1 point of Geistchild when activating Camouflage."

Freefire

"The player can fire their weapon without expending any ammo, even if the clip is empty."

Freefire is a Specialist ability that gives the player infinite ammo for a 20 second duration. When activated, your ammo counts are ignored for any weapons being used, and the magazine is reset to its max amount of ammo.

Ammo Carrier

"Nearby teammates receive a full clip of ammo when activating Freefire."

Similar to activating Freefire, players nearby the activation have their magazines reset to full.

Explosive Handler

"Give yourself and nearby allies 2 lethals while activating Freefire."

Fragmentation Skull

"Headshot kills cause explosive damage to nearby enemies during Freefire."

Marksmanship

"Headshots deal significantly increased damage while using Freefire."

Headshot hits are increased triple the normal damage of weapons.

Mk. II

"The player's weapon is upgraded while using Freefire."

Weapons can only be upgraded if the Ubersprengen (Pack-a-Punch) can upgrade the weapon currently as well. Any Easter Eggs that upgrade additional weapons must be completed to have this Mod work on them.

Squad Tactics

"Nearby allies get a headshot damage bonus while using Freefire."

Nearby players get a headshot damage bonus 1.5 times the normal weapon's output.

Suppressive Fire

"Enemies slow down momentarily as they take bullet damage while using Freefire."

Frontline

"Nearby zombies chase the user. The triggering player deals double damage to zombies for the duration of the special."

Frontline is a Specialist ability that pulls all zombie's targeting to the player activating, as well as double the damage output of your weapons for a 20 second duration.

Determination

"Gain 2 points of Geistchild when activating Frontline."

Hand-to-Hand

"Increased melee damage while using Frontline."

Damage is increased by four times the weapon's normal output.

Punishment

"While Frontline is active, weaker enemies die automatically after hitting the user."

Weaker enemies include Zombies and Pests. This mod does not lower damage taken.

Resilient

"Significantly reduces the delay before regaining health while using Frontline."

When your Specialist is active, health regeneration delay if halved.

Team Effort

"Nearby teammates also receive the damage bonus while using Frontline."

Players affected will only receive base Frontline damage.

Vicious

"Enemies take triple damage instead of damage while using Frontline."

All damage output is 1.5 times the normal damage output, stacking with Frontline.

Shellshock

"Creates a burst originating from the player. Knocks back nearby zombies, applies light damage, and holds them stunned."

Shellshock is a Specialist ability sending out a shockwave of energy (even through walls) and hitting zombies. Zombies are temporarily stunned, knocked over, and damaged as well, lasting for 12.5 seconds.

Breathing Room

"Shellshock has increased range and knocks enemies back further."

The range of your Shellshock is increased drastically, more than double the original radius.

Defibrillate

"Revive fallen teammates in range when activating Shellshock."

Exploit Weakness

"Enemies stunned by Shellshock take triple damage."

Enemies stunned will take 3 times more damage for all sources until Shellshock ends.

Fiery Burst

"Enemies hit by Shellshock are set on fire."

Protector

"Allies hit by Shellshock gain 1 point of Geistchild."

Sustained Zone

"Shellshock creates a zone of energy that lingers after the burst. Enemies that enter the zone are stunned, However, the range of Shellshock is reduced."

The shockwave turns into a zone that stuns any zombie that walks into the radius, including Wüstlings. While tame at first glance, this Mod can be vastly stronger paired with an active Totengriff (Insta-Kill), as zombies will be killed instantly entering the spawn.

Pairing this Mod with Breathing Room is advised, as the ample increase in range allows much more control over spawn points, shutting down whole rooms during Totengriffs, maintaining optimal SPH.

Universal Mods

"Channel Geistkraft to strengthen your natural abilities."

Universal Mods are secondary abilities benefiting the player and can improve strategies at a fundamental level. Each Mod has a buff that changes specific player interactions, while two interact with extra dealing damage to the zombies, and one affecting all players.

Armored Up

"Spawn and respawn with 3 points of Geistchild."

Discipline

"Increased weapon accuracy and damage while crouching or prone."

Dutiful Medic

"Take no damage from one hit while reviving a teammate."

Fast Hands

"Use items and lethal equipment faster. Increased damage for lethal equipment. Switch weapons faster."

Finishing Blow

"Deal extra melee damage against enemies with less than half health."

Flak Jacket

"Take no damage from your own explosives."

Explosions from Bomber (and their Bombs too) will not damage the player as well. 

Fully Loaded

"Moderately increased max reserve ammo capacity."

Ammo reserves are buffed by 50% for the player, rounding the number up to the nearest single digit.

Grenadier

"Carry twice the maximum amount of lethal equipment."

Tactical equipment is not affected by this mod.

Gung Ho!

"Fire weapons while sprinting. Increased shotgun damage."

Hoarder

"Carry an additional Blitz."

Long Lasting

"Power-ups last longer. Does not stack with other teammates using Long Lasting."

Any drop picked up with a duration, lasting six seconds longer.

Lucky Crit

"Chance to deal heavy damage when shooting a zombie's weak point, instantly killing regular zombies."

Mugger

"Increased Jolts for killing weaker enemies with melee only."

The player gains 20 more Jolts for every kill, if the zombie was damaged exclusively with melee. This includes any melee slot weapon received, excluding the Blade and Sword of Barbarrosa. Zombies damaged by anything else will not be able to reward the Mugger benefit.

Pack Mule

"Carry a third primary weapon."

Preventative Medicine

"Your whole team has longer bleedout time. This does not stack with other teammates using Preventative Medicine."

Players in the match have their last stand meter last for X seconds longer.

Resourceful

"Increased chance to spawn power-ups when killing enemies."

Resourceful adds one more drop to appear every round. This Mod does not stack with copies of itself. With this equipped, in solo, you will receive three drops a round, while in co-op, you will receive four drops a round.

Specialist Training

"The Special Meter requires less energy to charge than it would normally."

Specialist Training decreases the points needed to charge your Special Meter, lowering it by 300 Jolts after each use. This change is only a linear benefit, so in higher limits of Specialist uses.

Stubborn

"Keep all Blitz after being revived for the first time."