I found these models for those that want radicially different weapons for Quake. It only replaces the Shotgun, Super Shotgun, Nailgun, RL, and a few TF weapons. Sure, they look kinda shitty, but if you try them, they're much beefier sounding and looking than the default weapons.
I got the models from http://www.planetfortress.com/tfdone_easy/dox/index.html, but it had a ton of sounds that didn't sound Quakeish at all. I grabbed the weapon models (and two sounds) and put them in a brand-new .pak file so that it'll look and sound like regular Quake, but with some badass weapons. Sorry, but there's no replacements for the g/w models.
Extract to your /id1 folder. Change the pakx to whatever number is after the last pak file you have. Ex: If you have pak0 and pak1, you'd name the included .pak file "pak2", which it's called by default.