This will be the Spitter … uh, altered. D: Thanks to XvenomtakerX.
How to install Left 4 Dead 2 Naked Spitter:
Extract the “skin_c12spitter.vpk” file and move it into the “addons” folder (where you’ve installed the game, inside the directories “\left4dead2\addons”).
To remove the nude mod you just have to delete it from the folder where you’ve extracted the file “skin_c12spitter.vpk”, however you can also enable/disable the mod from the in-game menu “Extras” and then “Add-ons” without actually having to remove the file.