Overwatch Standard Issue Pulse Rifle
The OSIPR is essentially a Combine variant of current assault rifles, commonly issued by Overwatch Soldiers and Overwatch Elites. It has a 30-round magazine, which is reloaded with an automatic mechanism built into the weapon. A Dark Energy Energy Ball shooter is built into it; the orb is capable of disintegrating almost anything it touches. Only Overwatch Elite are allowed to fire the Energy Balls. On the body can be seen the alphanumerics "V952", also featured on other Combine devices.
The player first acquires the weapon at the end of Half-Life 2's sixth chapter, "We Don't Go To Ravenholm...", scavenged off of a dead soldier previously fighting stray Zombies coming out of Ravenholm. In Episode One, it can be found in a Combine supply room in the chapter Urban Flight. In Episode Two, it is found in a doorway in the chapter Freeman Pontifex, near a small overrun Combine outpost.
While similar, the mounted variant, the Emplacement Gun, is a different pulse gun. The OSIPR also bears similarities to the Submachine Gun, different in its smaller ammo capacity, higher damage and higher accuracy.
The OSIPR's recoil is extremely strong. The weapon's spread is much worse when firing the weapon in automatic mode, so firing it in short bursts is highly recommended (this also conserves ammo). Furthermore, the player can only hold three full magazines (that is, one in the gun, two spare), which are easy to go through if firing in automatic mode. OSIPR is best used in situations where nearby ammo is plentiful - that is, when fighting Combine Soldiers.
The cores powering the weapon's alternate fire are rather hard to come by and should be preserved for special cases. They are efficient on lined up enemies, since it goes through them all before it hits a wall. Using it in small rooms is also efficient, since it bounces on the walls, floor and ceiling. The cores are also known to be a one-hit-kill against even a Hunter (note that the Energy Ball is destroyed when it hits the Hunter). In addition, Energy Balls can be used to kill Striders but they only do around a third of the damage of the RPG rockets.
OSIPR-fired Energy Balls can be deflected by a blast made with the Gravity Gun, by capturing it. This happens whether or not the Gravity Gun is infused with the Citadel's Dark Energy.
 Behind the scenes
At one point in Half-Life 2's development, there were three assault rifles: added to the OSIPR, there was the AK-47 (or AR1) and the Incendiary Rifle that used a slightly different OSIPR model and functioned as a Flare Gun with a five-round magazine. The OSIPR was originally slated to be an OICW and would be the Combine's weapon of choice. All three weapons were finally scrapped. Instead, the Incendiary Rifle's model was turned into the OSIPR's, which became the only assault rifle in the final game. The OSIPR's model still uses the name of the original model ("v_irifle").
Several features from the OICW were recycled for the OSIPR, such as the reload animation used by NPCs: while the player reloads the weapon internally using an automatic system (with no model animation), NPCs are shown to reload manually and externally (with model animation). Furthermore, the OSIPR reuses OICW sounds when being fired by NPCs (this is also the case for the APC's pulse gun).
The player holds the OSIPR with only one hand. This is merely a design oversight.
Overwatch Soldier firing at Freeman with his OSIPR at Bridge Point.
 List of appearances
- Half-Life 2 - E3 2004 Trailer (First appearance) (Non-canonical appearance)
- Half-Life 2
- Half-Life 2: Deathmatch (Non-canonical appearance)
- Half-Life 2: Lost Coast (Non-canonical appearance)
- Half-Life 2: Episode One
- Source Particle Benchmark (Game files only) (Non-canonical appearance)
- Half-Life 2: Episode Two