From Lexicanum

The military term of Sergeant is used by human and Imperial forces such as the Imperial Guard and Space Marines to denote the leader of a single squad. Other races use various terms to represent the role of a squad leader.

• Sergeant in the Imperial Guard

• Space Marine Sergeant

Other Terms for Squad Leader

• Justicar - Grey Knights
• Sister Superior - Sisters of Battle
• Shaper - Kroot
• Nob - Orks
• Aspiring Champion - Chaos Space Marines
• Shas'ui - Tau
• Gue'vesa'ui - Gue'vesa
• Warlock - Eldar Guardians or Wraithguard
• Exarch - Eldar Aspect Warriors
• Sybarite - Dark Eldar Warriors
• Succubus - Dark Eldar Wyches