I made this Asset to GDT converter a while ago for someone, and they suggested I post it. I posted it.

It converts most simple asset types, like weapon files, into GDTs and allows you to create a new GDT to put them in or merge them into an existing GDT.

I made this really fast, so use with caution because things I make tend to have problems (backup GDTs before merging and stuff).

VERSION 1.5.1
  + Added CoD4 XModel importing
  + Automatically exports black vertices as white (can disable this in the customization section at the top of the script)
  * Bug fixes

  Due to a bug in v1.5, this update has to be downloaded manually. Sorry! The bug should be fixed in this version though

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This app exports XModels and XAnims (with notetrack support) from Maya 2012+,  and also has the same rigging and gunsleeve features that are in Treyarch's Maya 8.5 exporter. It can also import XModels from CoD5, and hopefully in future versions XAnims and from other CoDs too.

Note: Please inform me of any bugs found and I'll try to fix them

Installation

Note: If you have the old "CoDExportTools" version of this program, make sure to uninstall it first!

1) Download the script below and save it to My Documents\maya\<maya version>\scripts\.
2) In the same folder, create usersetup.mel (if you don't already have one). Add this code to the end of the file:

python("import CoDMayaTools");

3) Restart Maya

How to use

Everything is under the menu Call of Duty Tools at the top of the main window. Almost every button and object in the dialogs has a Tool Tip (mouse-hover text) that explains what it does, so check those for help.

Some people requested UGX to make a Script Placer.

So guess what. UGX made a Script Placer.

Virus Scans: https://www.virustotal.com/en/file/b8dd7e2aee5c0d1a6acc1d800338af501913fd09c2969b84567a6e6ffaa950c2/analysis/1407555843/
http://virusscan.jotti.org/en/scanresult/ddb7d6add74a20f6303d922558c7b099ddf8394f


This requires .NET Framework 4.0 (because I'm still using C# *sigh*), which you should probably have anyways. Don't expect this program to work correctly because nothing I make works correctly once its outside of my computer. 

I took it out of another project that I was working on that will never be finished because it's stupid. Fixed some stuff, added some stuff, and now it's done. Note: There are a few features that are always grayed out and you cant use them. Those are options that will default your map with a script such as Easy-Fx or Weather. The reason I can't make these work is because my CoD Root Folder is currently screwed up and I don't know why, so I can't test CoD Scripts. Anyways....

Some things I should point out before you use the program: Some options will need to replace existing files in your Root Folder to work. Those options are not required though. Any files that the Script Placer needs to overwrite, it WILL ASK YOU what it should do. Don't just spam "Yes" to any dialog box that comes up.

The Script Placer comes with a feature called "Map Remover" which helps you remove unwanted maps or files. It searches your root for files with specific names or contents based on the name of the map you are searching for. This is better than just regularly using the search bar in your root because it will only check common areas for files. That means it wont check places like raw\xmodels, which takes a while, for scripts, because they won't (shouldn't) ever be there.

The "Display Name" of the map is what is used in the main menus that the player of the map will see. So instead of seeing "Launch nazi_zombie_awesome", they might see "Launch Zombie Awesome". And other things like that.

Expect updates at some point or another. This program doesn't have an auto-update feature (because I'm lazy), so you'll have to download it again if you want the update.

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Changelog:
1.1.6:
- Removed placement of "sound,character,nazi_zombie_factory,all_sp" in mapname.csv which was causing a 1600 sounds error when trying to use a generated map with UGX Mod v1.0.x. This line has been added to dlc3.csv in the latest update to the UGX Modtools Patch (v1.0.6) which can be downloaded from the UGX Wiki. The UGX Mod Standalone dlc3.csv will overwrite the Modtools Patch dlc3.csv, eliminating the possibility for the character sounds to be included.

1.1.5:
- Fixed incorrect statement in _loadout.gsc

1.1.4:
- Fixed some DLC3 sounds not being included in created maps

1.1.3:
- Fixed loadout.gsc issues based on map prefix
- Fixed file name replacement in launcher files
- Lowered FX usage by removing unused weapons

1.1:
 - I made an update to this program to allow for selecting a custom root. Just click "Use Custom Game Path..." in the options menu. Select "Use Default Game Path" to use the default root. This program doesn't auto-update, so you will need to download it again. Its just one .exe though

1.0:
 - Initial Release