Important! Now Patch 1.2 available here: http://www.garrysmod.org/downloads/?a=view&id=132778

The pack includes:
Energineer with custom Gunslinger
Ninjineer
Vagineer (Necroborg) with custom Gunslinger
Dead Space level 3 RIG

It is an addon. You need skin switcher tool to shuffle through their skins.

Credits :
Valve - models
LEtheCreator - Ninjineer
Naughty_T - Ninjineer's skin
Riky69 - Energineer's Team Coloured Gunslinger, Necroborg Vagineer's New Team-Coloured Gunslinger
Sparkwire - RIG level 3
Striker - Energineer's skin
zocoword - Necroborg Vagineer's skin
SarisKhan - Energineer and Vagineer (Necroborg), hexing

You can see these characters in action here:
http://www.youtube.com/playlist?list=PL02C4BDE8DF02F1E0&feature=plcp
http://www.youtube.com/watch?v=x4ykGsJQjTI

All skins are copyright to their respective creators.