The Pulse SMG is a standard loadout weapon of Combine Grunts. These are used almost exclusively by the Combine, as a calibrated weapon requires gene coding to be operated. Alyx obtains one in the Northern Star by discovering one that is "unbonded" and still in the case. An unmodified Pulse SMG holds a 30-round pulse plug that must be reloaded manually by pushing it into the left side.
The SMG has 3 upgrades:
Reflex Sight: costs 15 Resin. Adds a blue holographic sight that is projected above the barrel.
Laser Sight: costs 25 Resin. Adds a green laser that is projected off the side of the weapon.
Extended Magazine: costs 30 Resin. Adds a vertical auto-loading magazine that re-inserts a full pulse plug after the weapon is depleted. The Extended Magazine holds three additional pulse plugs, and each one must be inserted manually.
When the Extended Magazine upgrade is equipped, it gains an underbarrel piece similar to the OSIPR's Energy Ball launcher, but it cannot be used by the player.
Despite its inherent compatibility with proprietary Combine Fabricator technology, Combine Grunts who use the Pulse SMG do not appear to have any of its tactical upgrades, only sporting the Extended Magazine.