There's two off perk weapons in the game so far, the katana and the flamethrower. I'm wondering if there's a negative benefit to having the two. Does it affect the way I play any class? Is there any downside to using them?
Currently, the only disadvantage of using the katana and flamethrower is that you don't get a class boost of any kind. I'm certain some kind of melee class will be added in the future to cover the katana though.
Other than this, they do have their uses. The katana, just like in KF1, is the best melee weapon due to its long range and quickness. As for the flamethrower, it obviously does something other weapons don't do: throw flames — great for lighting enemies on fire from a distance.
Off-perk weapons do not give you class exp. This means that as a Berzerker, you will not gain exp for the class with the Katana, which is an off-perk weapon (intended for the Martial Artist, who is not out yet).
However, off-perk weapons do technically have some use for the Demolitionist class. At rank 20 there is a choice between two perks, On-Perk and Off-Perk, the latter which adds bonus damage when using off-perk weapons.