Tier 1 Weapon(s):

Scout Rifle - the first semi-automatic rifle in the game. Slow firing but deadly in the hands of an experienced player. Effective at mid to long range.

Compact SMG - the first SMG in the game, extremely effective against clusters of zombies at close distances, but the effectiveness of the weapon decreases as the distance to the foe increases.

Shotgun - the starting weapon of several classes, like, for instance, the Hellraiser. An effective weapon to be used at close distance, especially against closely grouped enemies, as a single shell can damage or kill several enemies at once. Ineffective at longer distances.

Pistol - one of the most useful weapons in the game, due to the Pistol having an in-built silencer, allowing the players to kill zombies without alerting nearby enemies. Effective at almost any distance.

Machine Pistol - an automatic version of the pistol, lacking the silencer. The weakest of the Tier 1 weapon and one that no one should bother using, as there are more effective tools to start with.

Tier 2 Weapon(s):

Assault Rifle - the first assault rifle in the game. A weapon effective at all distances, against all foes, but not that useful against clusters of zombies do to slower rate of fire.

Sporting Carbine - basically an enhanced version of the Scout Rifle, a semi-automatic rifle effective at mid and long ranges. Ineffective against clusters of zombies at close ranges due to slow rate of fire.

SMG - the upgraded version of the Tier 1 Compact SMG. An extremely effective weapon for short and mid distances, capable of obliterating dozens of zombies in seconds due to high rate of fire. It becomes less effective as the distance increases.

Combat Shotgun - a modified, more effective version of the Shotgun. Capable of dealing more damage due to high rate of fire, but ineffective at anything than short distance.

Sniper Rifle - the first sniper rifle in the game. Extremely powerful at long distance, ineffective at short and mid ranges. A very situational weapon - if you have a good team that can protect you from zombies rushing your position, letting you focus on taking out distant enemies, it can be a valuable find.

Compact Shotgun - another Tier 2 shotgun, focusing on slower rate of fire, but more damage per shot and higher accuracy, allowing the weapon to be more effective at longer distances.

PDW - a peculiar fully-automatic secondary weapon, somewhat between a pistol and an SMG. PDW is more of a curiosity than a good gear - there are better weapons to choose from in the game.

Tier 3 Weapon(s)

Assault Carbine - the most powerful assault rifle in the game. Huge magazine, high rate of fire, good accuracy and high damage makes this weapon one of the best in the game.

Battle Rifle - a more powerful version of the Sporting Carbine, a semi-automatic rifle. When it comes to pure damage output, there are only a few weapons in the game better than the Battle Rifle. The weapon is effective at all ranges but falls off a little in close combat due to lower rate of fire.

Bullpup Rifle - another fully-automatic assault rifle in World War Z. When it comes to most of the stats, the Bullpup Rifle is less effective than the Assault Carbine, but it shines with Maximum Penetration - that stat is maxed-out from the beginning, making this weapon deadly against all foes in the game, allowing the players to fight effectively versus Bulls even if the foe's weak spots are not targeted.

Advanced SMG - the most powerful SMG weapon in the game. Huge magazine, extremely high rate of fire and overall good accuracy and handling makes this weapon one of the best in the game. The only problem is the lack of penetration, although it can be enhanced with certain upgrades.

Assault Shotgun- the best shotgun and one of the best weapons in the game. The Assault Shotgun deals insanely high damage from shorter distances, has large clip and maxed-out penetration. With upgrades the weapon's power is enhanced to absurdly high level, allowing it to be effective at mid-range as well.

Crossbow - another peculiar weapon. In capable hands it can be the best weapon in the game, due to the Crossbow firing explosive bolts - capable of taking out multiple enemies with a single bolt. On the other hand the weapon has slow rate of fire and long reload time, making it ineffective against larger groups of foes.

Primary Weapon(s):

Scout Rifle

Compact SMG

Shotgun 

Assault Rifle 

Sporting Carbine 

SMG

Combat Shotgun

Sniper Rifle

Assault Carbine

Battle Rifle 

Assault Shotgun

Crossbow 

Secondary Weapons(s):

Pistol 

Machine Pistol

SMG

Compact Shotgun

PDW 

Assault Shotgun