This is all you start out with. You're going to have to kill somebody with the crowbar and pick up his gun if you want something that shoots. You can also use the crowbar for more practical things breaking windows, prying things open or just plain smashing them apart.

Glock 9mm Pistol

Just your plain old 9mm pistol, don't waste rounds because you will have to reload. One shot, one kill. Additionally, you can hold down the alternative fire button to pop off a rapid succession of rounds at the sacrifice of accuracy.

.357 Magnum

This handheld cannon can easily rip a nice-sized hole through the enemy, and coupled with its "zoom" feature (alternate fire), can also be used as a great sniper gun. The only drawback to using this baby is the seriously skewed view you get from the recoil, but its fair fire-rate more than makes up for it.

Assault Shotgun

The shotgun is a Franchi-Spas 12 semi-automatic assault shotgun that loads from the bottom. Spread open some head with a barrage of led. You know the drill, but now you can see the walls turn to swiss cheese.

MP-5

The MP5's rapid-fire already makes it a formidable weapon, but its alternate fire, the "on-contact explosive" grenade launcher, makes it one of the most devastating weapons in the game. Aside from the mass genocide you create by using this weapon, it also comes with some really cool graphics that raise "immersion" to a whole new level. The MP5 also spits out tracers as it fires, so you can see where your firing in low lit areas.

Fragmentation Grenade

Hand-grenades are pretty standard in Half-Life. There is a three-second delay, so don't hold it too long or it'll blow your boxers off. It doesn't have a built in ticker, so you can be all sneaky with them and stuff.

Satchel Charges

The satchel charge can be easily slid across floors, or thrown into foxholes, windows and/or doors. Each charge is detonated with a radio device and their splash damage is larger and causes more damage than the grenades. Use extreme caution.

Trip Mines

Once set they emit a laser beam 90 degrees outwards. Once that beam is broken by anything, the mine explodes. They can be placed anywhere, including floors and ceilings.

RPG (Laser-Guided Rocket Launcher)

The rocket launcher is Laser-Guided which means wherever you point the guide the rocket follows. Kind of like a homing effect. Wherever the laser is set, that is where the target falls. You can opt to enable the laser targeting system, thereby giving away your position, or turn it off to conceal your location. The RPG's velocity is slowed down tremendously in water and acts like a torpedo.

Gun Turrets

There are big gun turrets and little gun turrets, but both can kill you. They're motion sensitive and will follow your movements around an area, spraying bullets at you with alarming accuracy.

Crossbow

Though it is not the most rapid firing weapon it is the most accurate. Used as primary fire, the crossbow has explosive tipped bolts (arrows) that explode on contact. It does a fair amount of damage, but the actual blast radius is far smaller than it appears. The crown jewel of the crossbow is in fact in its alternate fire - When switched into alternate fire mode, the crossbow becomes a sniper's dream.

Gauss Gun

An experimental, highly unstable weapon. One of the most important abilities is that it can shoot through walls, making it so that you can't take cover against it. The gauss's primary fire shoots out tiny spurts that are only effective in close to medium range due to its erratic spread. You can charge up the gauss by holding down alternate fire; the longer you charge it up, the stronger it gets. The longer you charge it up is directly proportional to the thickness of the wall you can shoot through. Lookout campers, retribution has come.

Gluon Gun

The Gluon gun (AKA "The Egon") is a prototype weapon developed by the Black Mesa Weapons Research Facility. It emits a constant stream of energy that disingrates anything in it's path. The Gluon Gun and the Guass Gun share the same ammo.

The Hive-hand

The hivehand has eight hornets to begin with, and automatically regenerates them slowly after you shoot them out. It's a great weapon for medium to long range, but once an enemy gets close enough, the hivehand is rendered almost useless due to its slow fire rate (after the initial burst).

Snark

Toss a few at these at an enemy and watch them tear flesh from bone. Make sure they have targets to attack though, because if none are found, they'll turn right back around and head for you. The Snarks explode after 10-15 seconds.