The Hunter is a Special Infected that can pounce and pin down Survivors, clawing at their abdomen until either the victim is dead, or the Hunter has been knocked off or killed by another Survivor. They are also extremely fast and agile, capable of quickly scaling walls. They have the least visible mutations, and can easily be mistaken for a Common Infected. Hunters are not the most physically robust Infected, having relatively low health, and thus it doesn't take very much to kill them.
When the Hunter crouches down in preparation to pounce, he growls, giving himself away to any nearby Survivors. However, whilst standing, he makes no noise. The Hunter is the only Special Infected that can remain absolutely silent. In Left 4 Dead 2, they can be killed with a melee weapon while in the state of pouncing by aiming upwards and hitting, although this is fairly difficult, as timing is vital and it's easier to kill them from a distance with a high-powered primary weapon.
In the second game his design changes