I fucking love the Plasma Gun. Almost as much as the Rocket Launcher. Almost.
and on-topic, I don’t believe there is a way past compiling and viewing in the Source Model Viewer. I don’t think any one 3D modelling program would have an option for viewmodels past maybe XSI ModTool.
It’s in the Source SDK directories. I’d say where, but it’s been too long since I last poked around in there for me to be sure.
You’d want to use the steam one cause if you don’t, when our wonderful friends over at Valve update the engine, the viewer won’t show you the proper stuff. The only legal use for a non-steamed sdk that I can think of is to be used on a computer without internet. But then you won’t be able to install Gmod anyway, so what would be the point? O_o