Here are some fairly simple Counter Strike NPCs to add to your Gmod.

Included are the 4 hostages, the 4 CTs and the 4 Ts. The hostages and CTs are friendly, (citizen AI) and the Ts are enemy (combine AI) and throw (2) grenades.

I couldn't find any CS:S NPCs so I decided to make these. The Ts and CTs were decompiled and then recompiled with combine & rebel animations, and the hostages used are just the standard models, because they were fine as they were.

YOU WILL NEED COUNTER STRIKE: SOURCE FOR THIS TO WORK PROPERLY - Otherwise, the CTs and Ts will be checkerboarded purple and black, (because they use the original cs:s textures) and the hostages will be error signs. (original model)

To install, just extract to your addons folder.

-EDIT- Whoops, I uploaded my beta version by accident. Here's the final version now, if you had it before I suggest you redownload.

-COMMENT- Wow, there's an interesting conversation going on here.
For all you saying this has been done before, sure, ok, I thought it was a pretty simple idea. But the reason I did it in the first place (as I've already said above!) was because I couldn't find any on gmod.org. So if you've got something to prove, just give me a link.
And also, to humour this one person, (xxXAcePilotXxx) it's kind of obvious valve gets credit for most of this. I mean, I've even said above that i just decompiled and recompiled the T and CT models, and since Valve made those, they get credit. If you think it through, it's clear. So credit goes to Valve
Wow, reply/rant over.