Scout

Space Marines noob in training. They have not yet gained the required geneseed organs or status to wear power armour. Usually organized into squads, and are the only marines capable of wielding sniper rifles. Black Templars do not use scout squads, instead mixing their scouts ("initiates") into their normal battle-brother squads. They apparently think this gives the initiates better experience, but it's really just because they make amazing meat shields.

They are lead by a sergeant (usually a member of a tactical squad that chose to impart his wisdom on a younger generation).