Daemonhunters
Daemonhunters are a branch of the Imperium's Inquisition specifically for hunting the manifestations of the warp. These are further divided into Inquisitors and a special form of Space Marines known as the Grey Knights. The Inquisitors can be found surrounded by many different branches of the Imperium's Militant forces due to their ability to call on local governance for support.
Daemonhunters used to have their own dedicated codex, however a certain bearded little fuck decided it needed more Spess Mahreen and less awesome and thus renamed it Grey Knights. The same fag then butchered whatever fluff they had so he could jerk off to his own filthy creation.