OBJECTIVE-STYLE WALL WEAPONS TUTORIAL
I will show you how to make the special objective-style wall buys like you've seen in Tank Yard without asset manager.
WHAT YOU NEED
Notepad++ [You are not allowed to view external links. Register or Login to see them]
(obviously) Your mod tools
The following steps will take you through Notepad++ and Radiant.
STEP 1: Notepad++
Locate your weapon's world model in your root/raw/xmodel folder. For this tutorial, I will be using the MP40.

STEP 2
Make a copy of the xmodel file and rename it to whatever you want (I suggest just adding "_obj" for objective.)
EXAMPLE: weapon_zombie_mp40_smg_obj

STEP 3
If you've installed Notepad++ correctly, you can open the file by right-clicking and clicking on "Edit with Notepad++."

STEP 4
You should see this:

Now replace each of the "mtl_"... whatever your weapon is... with "mtl_weapon_explosives_obj" like so:

Press Ctrl+S to save the file.
BONUS STEP
Now if you want to see what it will look like in game (non-animated), open it up in Asset Viewer and look for your file for a quick preview.

STEP 5: Radiant
The wall buy is the same as any of the wallbuys in the past with an extra step.
I assume all of you know how to setup weapon wallbuys.
In this case, however, I will use the prefab for the MP40 wallbuy.
I have stamped the prefab and deleted the chalk.
I've also deleted unneeded kvps that have to deal with the chalk.

STEP 6
Select the script_model and press the Spacebar to make a copy.
Move it so the copy and the script_model are in the same position.
STEP 7
If not already shown, press the "N" key to show your entity KVPs.
Rename the classname KVP to "misc_model" and delete the targetname and target KVPs.
Click on the model KVP and you will see the "..." appear. Click that and look for your "weapon_..._obj."

Be aware that the "_obj" model is invisible because for some reason Radiant makes it that way.
Now save your map, compile, and test it out

This tutorial was originally requested by fatboypro.