Check to see the normals are pointing the right way (go into textured view > if anything shows up transparent, the normals on those faces are pointing the wrong way). Sometimes recalculating normals doesn't work properly (the algorithm isn't perfect). If you see any faces that have incorrectly oriented normals, select those faces and manually flip them.

I actually don't know much about particle effects, sorry! Try asking the polycount forums. There might be someone there who can help.

Is the issue that the model is rotated weirdly? You can try to start a fresh scene, import a fresh rig (weapon_bone), import your model and try again. It might just be that you accidentally rotated the bo

You could also try resetting the rotation/scale/location of the model from object mode (select your model, press ctrl+a, select rotation and repeat for location/scale).

In the UV window, click new, enter in 1024 x 512 (this is 4x the size of your final texture size), then unwrap your model. You used to be able to unwrap to half the square, but that no longer works.

Well I'm stumped. I've never seen this happen before. Try using an older version of blender (something like 2.66).

Once you post an item to the workshop, click edit description, then you'll use the [img]<link to picture>[/img] tags.

Example: [img]http://i.imgur.com/I0DlCYT.jpg[/img]

This explains how to install it step by step: https://developer.valvesoftware.com/wiki/Blender_SMD_Tools

Once you download blender-2.71-windows64.zip, unzip the folder and open the blender application. From there, follow the steps listed in the link.

Don't download the installer. Download the zip file.

I've never seen this happen before. What version of blender are you using? And are you using windows or mac?

Never use subdivision in tf2 modeling. There is no reason to.