Here's a list of all the weapons you will be using in Half-Life - Opposing Force to kill those aliens and Black Ops

The Weapons
Name Description Picture
Wrench Like the Crowbar in Half-Life but more powerful. It has a powerful secondary mode to speed up breaking those boxes.
.357 Desert Eagle Like the Magnum in Half-Life, it has one-shot kill capabilities, but also has a secondary mode of laser-sight.
Pistol There's not much to it really, it's just a pistol. Pistol
Machine Gun One of my most used weapons, the machine gun has a secondary mode as a Grenade Launcher. Machine Gun
Shotgun A pretty powerful weapon but very inaccurate at long distances. Shotgun
Grenade Need to kill a big group of enemies fast? Grenade them! Grenade
Trip Mine Once placed these emit a laser which, when broken will explode the mine. Trip Mine
The Rocket Launcher It is very good at killing lots of enemies at once and shooting down Black Op helicopters Rocket Launcher

Satchel Charges

Very powerful Explosive devices which are detonated by Remote.

Satchel Charge

Barnacle Gun Need to get across a large gap? You need a Barnacle gun. These will latch on to anything alive, so as long as there's some sort of life form where you need to go, you can get across with ease!
M-249 SAW A very powerful machine gun which is best used while crouched.
Displacer This weapon will shoot portals at your enemies. It's secondary mode allows you to teleport to the Alien World for Health and Supplies. Word of warning though: the Secondary mode uses ten times the amount of ammo as using normal mode does.
Shock Rifle An alien weapon used by Shock Troopers. It is quite powerful.
Spore Launcher This weapon shoots Spores which blow up when they hit their target