It's a chainsaw.
I'm aware chainsaws don't fire bullets, thank you.

This one would be more complex to implement than a "simple" reskin and it's certainly not helping it for beeing selected.

The chain is animated, I made a loop animation for it, but i didn't find how to make it work in-game.
I've added a video of the view model chain (slow) animation. You can see how i faked a chain loop by just making pop few chain links segment to the next during few frames. This way i didn't have to rig and animate each link during the full loop, which wouldn't have been great performance-wise.

I didn't really have a plan on how it should work, but imo, if it's powered like instant kill, it should replace both primary and secondary weapon, and probably have a charge or a fury.

It is team colored (just can't find my picture of it). It's not paintable as this system wasn't in place by then but i can look into it.

There are 2 models, one for the world view and one for the first view. I know Valve doesn't use that system anymore, but if i use the world model in first view, it really doesn't look great.

And I still thank Ezvier for the name !