Just thought I should mention it, in case no one else has… There’s a rather serious bug with the Black Mesa security guards. They’re completely incapable of defending themselves if whatever they’re fighting is sufficiently close to them. This applies to both hostile NPCs and the player (if the player provokes them into attacking).
Basically, if whatever they’re attempting to fight is close enough, the security guards will stop shooting and stand there with their weapons aimed indefinitely. If a zombie corners one, they’ll just stand there and let the zombie continuously swipe at them. If you’re the kind of player that likes screwing with Black Mesa personnel, you can simply run up to security guards to prevent them from being able to fight you. I don’t know if it’d be better to let them shoot at point-blank range or add some kind of melee system like the HECU marines have, but something should really be done about that… 