To begin with making your own kinect-enabled humanoid ragdoll, you will need an original Half-life 2 character to decompile. You will need to extract a character (I used and suggest the Combine_Super_Soldier) from Garry's Mod's .GCF file.
Extract all relating files to a usable directory, then decompile these (I suggest using MDLdecompiler) to a new directory. this will be your Working directory.
You will possibly need to tweak the .mdl if it does not decompile first time. Open up the character's .mdl file with Notepad++ and edit the very first line on the top of the file. It will look like "IDST0" or at least a number where the "0" is. Change the number to a comma, it will now look like "IDST,". Save, and attempt to decompile.

You can now import the model's Reference file into your 3D Program. It is in .smd format.
Rig up your character, but also keep in mind that you can resize your rig to your model if needed, even if you have a small character you can resize the rig to their size. This will not affect the final result negatively.

You will need to export two files, first one being the Reference model, to replace the original reference model, in .smd format. Export over the original.
Now you will need to export the Sequence .smd file. Export this over a file named ragdoll.smd and replace it.
Check the .QC file to make sure everything is in working order. You will need to change the destination of the .mdl and the materials folder if you plan on making a new ragdoll.
Go ahead and compile after you have finished editing the .QC file.

Now you can test it out. Plug in your Kinect Device before entering either singleplayer or a multiplayer match, or however you have your model set up to the game.

Once loaded in-game, spawn the model, hold down C for the Contextual menu, and right click your ragdoll that you have made. If your Kinect is detected then you should see an option of "Enable Motion Controls" or so. If not, read through this Wiki Entry for Garry's Mod and Kinect.

Once you have enabled that option, you will see a prop of the kinect appear infront of you. this will behave like a stage setup. Stand back into its view and you should see your model begin to motion with your movements.
If you have any issues with the model not responding to your movements at all, or even standing up, give the wiki entry a readthrough http://wiki.garrysmod.com/page/Kinect/using Make sure you have not missed any required software.

If working, then you can repeat the previous steps for any more characters you want to make usable with the Kinect!