Sidearm
From Halopedia, the Halo wiki
Sidearms in the Halo Universe are a class of weapons that play both a primary and secondary role in combat.
List of Sidearms and their strength
M6 Pistol (Unknown) M6D Pistol (H1: Strong / H3: Unknown) M6C Magnum (H2 (Pre-Update): Weak / H2 (Post-Update): Very Weak) M6B Pistol (Unknown) M7 Submachine Gun (H2: Average / H3: Unknown) Energy Sword (H2: Very Strong / H3: Unknown) Needler (H1: Average / H2: Very Weak / H3: "Strong") Plasma Rifle (H1: Strong / H2: Average / H3: Unknown) Brute Plasma Rifle (H2: Average) Plasma Pistol (H1: Average / H2: Very Weak) Brute Spiker (H3: Unknown)
Modern definition
A side arm is a small personal weapon that is typically worn on the body in a holster in such a way to permit immediate access and use. Although this term can apply to swords and other mêlée weapons, the modern use of it usually pertains to pistols and similar firearms.