Alias pws "pws1"
alias pws1 "s ;alias pws pws2" //shotgun
alias pws2 "as ;alias pws pws3" //autoshotgun
alias pws3 "r ;alias pws pws4" //rifle
alias pws4 "hr ;alias pws pws5" //sniper
alias pws5 "smg ;alias pws pws1" //smg

alias s "sv_cheats 1;give pumpshotgun;sv_cheats 0"
alias as "sv_cheats 1;give autoshotgun;sv_cheats 0"
alias r "sv_cheats 1;give rifle;sv_cheats 0"
alias hr "sv_cheats 1;give hunting_rifle;sv_cheats 0"
alias smg "sv_cheats 1;give smg;sv_cheats 0"

alias ews "ews1"
alias ews1 "pb;alias ews ews2" //pipebomb
alias ews2 "m;alias ews ews1" //molotov

alias pb "sv_cheats 1;give pipe_bomb;sv_cheats 0"
alias m "sv_cheats 1;give molotov;sv_cheats 0"

bind "f1" "pws"
bind "f3" "ews"
bind "f2" "sv_Cheats 1;give pistol;sv_cheats 0"
bind "f4" "sv_cheats 1;give first_aid_kit;sv_cheats 0"
bind "f5" "sv_cheats 1;give pain_pills;sv_cheats 0"

Step1, editing whitelist.cfg:
- Use the Vpk extractor on pak01_dir.vpk and extract everything in the left4dead folder.
- In the left4dead folder, open the file whitelist.cfg with notepad. This file tells the game in which folders it can look for custom things. You'll see a line like "add" "materials/console/...". Add this to the whitelist.cfg file:
"add" "materials/models/..."

Now the game can look for custom materials in that folder too, but that alone doesn't do it, the game will still use the materials in the vpk files if they are available there. For example, lets say we want to edit the pistol's texture.

Step2, editing pak01_dir.vpk:
- Right click on pak01_dir.vpk and open it with Notepad++. Look at the first few lines, look familiar? It should, it's identical to the content of the .vmt files. This is what tells the game to use the materials from the vpk files.
- We want the pistol, so do a search for v_pistol until you find the following block of text:
materials/models/v_models/pistol/v_pistol_reference
{
$basetexture "models\v_models\pistol\v_pistol_reference
$bumpmap ....
...... etc
}
- You can do 2 things, you could remove that entire block of text and save the file, it does no harm but if you remove something too much it could lead to errors so I don't recommend it. A safer way, do some renaming. Change the basetexture line in the above block of text to:
$basetexture "models\v_models\pistol\v_pistol_reference2
- Rename the vtf file in your materials folder to v_pistol_reference2.vtf

Now the game will look for v_pistol_reference2.vtf in the vpk file but obviously won't find it. Since you allowed the game to look in materials/models folder for custom content, it will find the file and use it from there.

http://i35.tinypic.com/2ivd98x.jpg

In the lower part of the pak01_dir.vpk file you'll also find model info, you might think this but you can't add custom models by removing or editing anything there. Do NOT change any of the model info in this file unless you know what you're doing.
You can change view and world models by editing the weapon_ script files in the left4dead/scripts folder. Look for the "viewmodel" line. But don't get your hopes up because you won't get custom models to work without serious errors.
Modderfreak, you say you've decompiled and recompiled L4D weapons before, then you must have noticed the "animation is out of bounding box" warning on the weapon bone. The result is that the model appears outside the screen when you recompile it. If you fix this warning by editing the smd files in notepad then you completely mess up the animations since all animations are affected and you have no way of knowing the correct position of this bone.
I'm still trying to find a way around it but right now it looks like we're going to need a new mdldecompiler