Perks are classes in Killing Floor that allow players to have specific roles and capabilities that level up with specific tasks such as dealing damage with the perks specific weapon class and killing certain specimen.
Killing Floor Mod Perks
For more information, see: Killing Floor Mod Perks
The original versions of the mod had no perks, and when they were eventually added they did not function quite like they would in later games. You first had to unlock each individual perk by completing a task, and the perks did not level up.
The available perks were:
Killing Floor Perks
The retail release of Killing Floor had all the perks unlocked from the start, but they could now level up (from level zero up to level six). They also added two new perks with Demolitions and the Firebug. Medic was also renamed to Field Medic, and Support became Support Specialist.
Killing Floor: Calamity
For more information, see: Killing Floor: Calamity Perks
Killing Floor: Calamity features the same perks as Killing Floor, but each has their own super move now.
Killing Floor 2 Perks
In Killing Floor 2, perks can now level up to 25 and are given a choice between two different talents every five levels. Each class also now features a unique knife and grenade. Three new perks were added with the inclusion of the Gunslinger, SWAT, and Survivalist. Demolitions was also renamed to Demolitionist.