The 9mm Semi-Automatic Pistol, commonly referred to simply as the 9mm Pistol, is a weapon featured in Half-Life and its expansions. The standard issue weapon used by the Black Mesasecurity guards, it is one of the most commonly used weapons in the series. It can be fired in either semi-automatic or automatic mode.
If fired in semi-automatic mode, the Pistol is one of the most accurate weapons in the game. While it does little damage per shot, it has good accuracy even after multiple shots in a row.
Because of its accuracy, it is best used at long range. Most enemies have poor accuracy at long range, which puts the player at a major advantage.
When firing at long range, aiming for the enemy's head is advised, as headshots do triple damage. This works very well against enemies that have high health, such as the Bullsquid.
This weapon shares ammo with the MP5, which makes it very easy to find ammo for this weapon throughout the game.
The Pistol is one of the few weapons that functions underwater, therefore it is a good choice to use against the Ichthyosaur if one wishes to conserve Crossbow ammunition. However, it takes longer to kill an Ichthyosaur with the Pistol than it does with the Crossbow.
It is best used when an enemy unexpectedly appears while firing at long range. Its rate of fire is fast enough to kill an enemy at short range without too much trouble.
It also works well as a makeshift SMG before the player obtains one. However, they should make sure to reload often, as this mode quickly eats up ammo.
Even if one shot is fired in rapid fire mode, it will be less precise than in semi-auto mode, thus making the rapid-fire mode useless for precise shots. This does not apply for Opposing Force, where accuracy remains unaffected.
The Pistol was originally to have an attachable suppressor. Scrapped in the final version, the attachment and detachment animations are still in the model file. It is unknown where it would be obtained. As the suppressed Pistol is used by female Black Ops as their primary weapon, it is likely it was to be acquired through killing one.
One of the early Half-Life demonstrations shows that the Pistol used the suppressed firing by default, had the slide to be pulled again after reloading, and had a 12 magazine capacity instead of 17.
An early texture for the Pistol featured in the Half-Life SDK files shows it was first to be a Glock 18. This may explain why the final Glock 17 has semi-automatic and full-auto modes: that feature is seen in the Glock 18 only, and was probably kept after the gun model was changed.
Similarly, Team Fortress Classic's Sentry Guns use the unsuppressed Pistol firing sounds.
In Half-Life and Opposing Force, a small glitch with the Pistol exists: it can be reloaded at any time, even with a full magazine. The most likely reason for this is because the magazine size of the Pistol was reduced from 18 to 17. Furthermore, although the gun retains the 17 bullet magazine in the retail version of Blue Shift, the glitch cannot be performed.