Yes, yes I know a lot of you know how to do this but the newbies for VHE don't
So here I go, it will be pretty damn short because it isn't that difficult.
First, get the models you want. As in a new Gauss, Egon, shotgun,etc.
Then when your working on your map spawn the weapon that you want to replace(as in spawn a weapon_Gauss) and go to it's properties page and scroll down in till you see "Custom Model" or something like that, and press the button besides the bar and search for the model. Make sure you made a folder of your map name and place it in models with the weapon model along with it.
That will work if it doesn't wtf did you do
Just for the hell of it.......here are some models that you might like.
Note:I did make any of these models, I found them on Sven Coop forums.