this is a curious one, in one of the latest leaks is a bunch of earlier manhack textures for all different versions, including retail styled and the earlier 2001-ish manhack, but besides those is a texture simply called "basetext" that doesn't bare resemblance to any version previously known so I decided to have a shot at recreating it!
Its blade can also be used as a weapon once its killed!
To install, navigate to the local files of half life 2 (through steam), then in the hl2 subdirectory (there should be one for platform aswell) create a folder called custom and put the extracted "manhacktext" folder in the custom folder.
then start half life 2, if the changes do not appear try restarting steam.
Prototype_Manhack_.zip
Key Authors
Uncanny
Modeller, texture artist, animator
Original Authors
Valve
Original textures, Animations
Version
1