north moat
OK, here is how to reskin a new gun the @north moat way which is the right way but needlessly complicated and more painful.
I will edit and clarify things as needed, but I expect everyone to start posting reskins of their favorite weapons after this post.
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Tools. You will need ucc.exe/lcc.exe and HTK (for extraction), and a image editor of your choice (I suggest gimp). you will need to have UnrealEd.exe (and honestly you should have the entire suite of Deus Ex Modding tools)
Setup. install HTK to DeusEx/System where ucc.exe/lcc.exe, make a package (or folder) for your mod. Make a text file and rename it AllWeapons.uc, and rename another textfile to WeaponYourWeaponName.uc and ensure it is in your package/Classes.
Extract. Open UnrealEd.exe and export all classes (upper right under browse select classes, on the lower right click the Export All button). Under browse select Textures from the dropdown, and DeusExItems from the middle dropdown. Navigate to and select the textures that correspond with your the weapon you are reskinning and click the export button. Export them to your package/Textures.
using Powershell navigate to ucc.exe/lcc.exe (in DeusEx/System) and run .\LCC.exe fullbatchexport .\DeusExItems.u .\Models this will export all models to a folder in system called Models. Move any models for weapons you wish to reskin to your package/Models.
Transform. In package/Classes/AllWeapons.uc define the class as class AllWeapons2 expands AllWeapons abstract; and copy the exec definitions for the player view version, 3rd person version, and pickup version of the weapon you would like to reskin. in package/Classes/AllWeapons.uc replace references to the models to the ones you have extracted to your package/Models, and replace the textures with the ones in your package/Textures (the paths are local to your package folder, so something like ANIVFILE=Models\StealthPistol_a.3d should work just fine). Change the name of MESH= and MESHMAP= . Pay close attention to the names.
In package/Classes/WeaponYourWeaponName.uc define the class as class WeaponYourWeaponName extends and then the name of the weapon class you are reskinning, like WeaponCrowbar You can find these in Deus Ex/DeusEx/Classes. Define defaultproperties for this class and redefine PlayerViewMesh=,PickupViewMesh=,ThirdPersonMesh= to the coresponding LodMesh'package.MESHMAP' where 'MESHMAP' is whatever you defined your MESHMAP= to be.
Use your image editor of choice to modify the images in package/Textures. Ensure the names of the files match the names refereced by AllWeapons.uc