Is it possible to have a swep that messes with the players running and walking speed?
Yes if your making it then you can put something like this in your server file/section.
for running speed
self.Owner:SetRunSpeed(X)//x is how fast they run default is 500
self.Owner:SetWalkSpeed(X)//x is how fast they walk 250 is default
Lol I meant to say like when a person is shot from the weapon there walk speed and run speed are slower.
Lol when you should take more time into explaining what you want.