The TTT1 Version of the infected from the Town of Terror has the infected use a weapon called "claws". The left click is an attack like the knife, and the right click is a leaping ability. You can see it in action at this timestamp here in this video, or alternatively you can imagine the Half-Life 2 Fast-zombie's leap on a right click.
I would try to use the code that Town of Terror uses and merge with the Knife in this mod, however there is no source available as far as I can tell.
The TTT1 Version of the infected from the Town of Terror has the infected use a weapon called "claws". The left click is an attack like the knife, and the right click is a leaping ability. You can see it in action at this timestamp here in this video, or alternatively you can imagine the Half-Life 2 Fast-zombie's leap on a right click.
I would try to use the code that Town of Terror uses and merge with the Knife in this mod, however there is no source available as far as I can tell.