The alien infantry forces of the Universal Union in the flesh...or metal...or synthetic material of some kind...Anyway, Opposing Force 2 synths! This skin replaces the standard Combine soldiers, prisonguards and Elites. Soldiers and prisonguards have the same tan skin reminiscent of the Combine's other synths (i.e. the Strider) while the Elites have a blue skin more akin to the Hunters in Episode 2. I have no skill in texturing whatsoever, so unfortunately the eye glow of the shotgunners are the same as the normal infantry.
If you want to pretend more easily that your alien invaders are in fact invaders from another world, use this to replace their voices.
Credit to OF2 Dev Team. All I did was port this to HL2.