Stalker

Stalker(Hunter)
Stalkers are B.O.W.'s made of crossing human with reptile and adding the virus(Glimmer and Gamma were amphibian-based though). They are toughest non-boss enemies, behind only Crimson Head. They are separated in various types:

Stalker Alpha
Those are the basic stalker type. They have higher HP than Tonguer, and they are able to perform a jump attack, dealing high damage. They are faster than zombies but slower than crimson heads.

Stalker Beta
Slightly stronger variant of Stalker than Alpha, able to deal more damage. They also possess jump ability.

Enhanced Stalker
Those are upgraded variant of Stalker Alpha, they deal a little more damage and endure a bit more damage. They also possess jump ability.

Elite Stalker
Those have highest health of all Stalkers, making them the "tank type". They also deal more damage than most of stalkers due to their big claws and they possess jump ability.

Glimmer
Their health is lower than that of other stalkers, however they are able to spit acid, which makes them dangerous enemy. Good choice for player zombies who want to play safely.

Stalker Gamma
Their health is about that of alpha stalker, but instead jump ability they have tongue-grab ability, much like tonguers. Gamma's tongue attack however, is much more deadly - when they drag you to themselves, they kill you instantly by swallowing you. Good choice for player zombies.

Tick
This one have health similar to most of the stalkers, but it's melee attack is poisonous and it's able to spit acid, making it a very dangerous enemy. One of best choices for player zombies.

Sweeper
Poisonous variant of Enhanced Stalker, the only differences of Sweeper and Enhanced Stalker are color(Sweeper is red) and the fact Sweeper's melee attack is poisonous, making him a dangerous enemy, especially when combined with it's jump ability.

Farfarello
This stalker type have average health and no jump ability, but it's able to render itself invisible, making it impossible to target with auto-aim, forcing player to either click shot or use specials. They appear bigger than other stalkers.

R Stalker
This stalker is similar in statistics to alpha stalker.