Alien Swarm/Weapon one and Weapon two

Alien Swarm is rife with various tools, weapons, and miscellaneous items that can help you destroy the Swarm, heal your allies, or a myriad of other special effects.

Upon selecting a campaign to play, players are prompted to select both their character and a choice of two primary weapons, as well as a single secondary weapon. The two primary weapons can be changed at will; the secondary item is used by pressing the 1 key.

Aside from the left mouse button, which uses the default fire mode (for example, the standard assault rifle simply shoots bullets), it is possible to click in with the mouse wheel to execute the weapon's alternate firing mode, assuming it has one (for the above example, the assault rifle would fire a grenade which detonates on impact with a target or the ground). Right-clicking allows players to execute a melee combo attack which is effective against enemies too close for enemy fire. Much like other Steam games, friendly fire cannot be disabled, and on higher difficulties can be the bane of players. Using the melee prevents friendly fire.

When a reload order is issued, either through running out of ammunition in your given clip or manually (R by default), a small gauge appears at the centre of the screen. Hitting R when the cursor is over the white highlighted section of the bar will prompt the character to perform the reload far faster than usual. It is accompanied by a white flash on the weapon's muzzle and possibly a character quote. Failing to hit the reload button at the right time causes the weapon to jam and become unusable for a longer period of time. Avoiding the reload button entirely performs a standard reload. This fast reloading method is necessary to obtain the Quick Reload and Gunslinger achievements.

Players can carry two primary weapons and a single secondary item at any given time. It is possible to exchange these items, or press G to drop a given primary weapon. This is most useful if it is out of ammunition.

M42 Vindicator
The Vindicator is the first shotgun available in the game, but it is restricted to the Officer class only. That said, however, the Vindicator is the ideal combat shotgun, boasting a far higher rate of fire and magazine size than the standard-issue version. It also sports incendiary grenades which can let it replace the flamethrower in some circumstances. Overall, the Vindicator is a highly effective and deadly weapon, effective at short and medium range.

Official Description: The M42 Vindicator is a pneumatic assisted pump-action shotgun with a dual, selective magazine system. IAF standard ammunition loadout provides for 12-gauge rounds in one magazine and a number of timed incendiary grenades in the other. The Vindicator is only issued to NCO rank marines.

S23A SynTek Autogun
The SynTek Autogun is a hi-tech squad automatic weapon of the Alien Swarm universe. Similar to the M56 Smart Gun found Aliens versus Predator, it's large magazine allows for sustained fire and it features a target tracking device that offers auto aiming for multiple targets. However, its weight slows the user down and it is only available to Special Weapons class. While its modest rate of fire makes it quite capable at handling all but the largest swarm attacks, it is not as efficient at taking out larger swarm creatures. Best used at medium to long range to make full use of its auto aiming capabilities.

IAF Minigun
The Minigun does the same amount of damage as the autogun, but its rate of fire is greatly increased. While it may not have auto targeting like the autogun, it can deliver a hail of fire that can overcome even the most concentrated drone attacks, and quickly take down large swarm creatures. However, the wide spread of fire means you have to get close to large swarm creatures for all shots to hit and its lack of auto aim and high rate of fire means your ammunition being quickly depleted. The gun requires a spin up, making you vunerable to surprise drone attacks and being overkill for taking out one or two drones. This weapon is best used when playing on insane difficulty where drone attacks are large and numerous.

IAF Medical Gun
A piece of equipment that medics can use instead of the healing beacon. Aim it at a injured marine and it heals them. You can also heal yourself with alt fire. Good to heal while keeping the squad moving, but can only heal one marine at a time. The medical gun cannot be reload and is discarded once it is expended.

22A7-Z Prototype Assault Rifle (Technician)
A rifle restricted to tech marines. Primary fire functions identical to standard issue assault rifles, but with added auto aim. Instead of frag grenades for its secondary fire, it fires stun grenades. Useful for getting yourself or a teammate out of a pinch without the punishing friendly fire.

22A3-1 Assault Rifle
Standard issue assault rifle available right off the bat. Rounds don't do much damage, but is offset with its decent rate of fire. Secondary fire mode fires the attached grenade launcher and is one of the few explosive ordnance available for low levelled players. Best used against drones while still lending a hand at taking down larger targets. A versatile weapon useful throughout the whole campaign.

M73 Twin Pistols
Two handguns used together. Each handgun bullet does more damage than a standard assault rifle round but with only 24 rounds, meaning more time being vunerable while reloading. The twin pistols is the only weapon that can be fired without movement speed penalty. All other weapons available will cause the user to lose speed when they fire. A good aim and being able to fast reload consistently is required to make the most of twin pistols.

Model 35 Pump-action Shotgun
A very powerful shotgun available for all classes to use. Does more damage than the vindicator, it can take out large swarm creatures with a few solid hits. Unfortunately, it is hampered with its small magazine size and the maximum amount of total ammunition carried. Nevertheless, it is still one of the most powerful weapons available for low levelled marines.