(Prototype) Assault Rifle
A weapon overlooked by most experienced players due to being the first gun in the game, it is nevertheless a very capable firearm. Doing more damage per round than the autogun, it requires half as much ammo to top off from an ammo satchel. More importantly, it has a grenade launcher with 5 grenades (Stun grenades for the prototype rifle, explosive grenades for the regular rifle), which can save you from a tight spot, especially the stun grenades, as they deal almost no damage to teammates. Best suited for characters who have a damage bonus (Bastille, Crash, Wildcat, Sarge). The prototype's rifle autoaim can be useful for killing offscreen swarm (Watch for the laser twitch) and detecting swarm in dark environments.Tesla cannon
Previously the most powerful gun in the game, it has long since been nerfed. Still, it remains useful as a secondary weapon due to its amazing stun capabilities and utter lack of friendly fire damage. Shield bugs in particular become extremely easy to dispatch after being hit even with even the shortest tesla cannon zap. Make sure to use small consecutive zaps, rather than continuous fire, to conserve its limited ammo. Zap infested teammates to slow down infestation rate.Vindicator
This officer-only gun is a paragon of destruction. Holding 14 shells, it can stop a swarm charge on all but the highest difficulties and still have some shots left before having to be reloaded. The 5 incendiary grenades it holds for secondary fire can be a godsend for when you don't have a flamer to burn some biomass or a cluster of eggs. The grenades are on a timer, but will explode immediately if they hit a swarm before coming to a stop. PROTIP: if you are going to die due to parasite infestation, shoot a grenade or two at your feet, and the newly-hatched parasites will meet a timely end. It takes a pro to kill the parasites that killed you.Autogun and minigun
These bad boys can only be handled by the burliest and/or fiercest members of the team, i.e. the special weapons specialists. What they lack in features and damage per shot, they make up for in their ability to pump out a lot of bullets in little time. The autogun has autoaim and does not require any spin-up before firing, unlike the minigun. The minigun, however, deals a lot more damage, making it more useful at higher difficulties. Special autogun ammo crates are scattered throughout levels, so make sure to remember where they are to avoid having to explain why you left the team with no ammo. Carrying these will slow you down, but only when they are held. Putting it away will allow you to move at full speed.Twin pistols
Semi-automatic sidearms that can fire as fast as you can click. They can be fired and reloaded while running, which can be useful. Make sure to resist the temptation to start rushing when wielding those.PDWs
Personal defense weapons are a pair of SMGs that deal the most damage per second of all firearms in the game. To compensate, they chew through ammo at an incredible rate. Truly devastating in the hands of a character with a respectable damage bonus.Pump-action shotgun
Does significant damage at an acceptable fire rate, but only holds 4 shells, resulting in frequent reloads. Does more damage than the Vindicator. Requires a lot of ammo to get through an average mission. High spread. Good as a secondary weapons or a primary if your squad can afford the ammo consumption.Sniper and rail rifles
These deal a lot of damage per shot, but are limited by their firing speed. The sniper rifle is equipped with a scope that lights up swarm in green, but obscures an area around your target; the scope is activated by secondary fire. The rail rifle only holds 1 round, forcing you to reload after each shot; if you choose to use it, make sure you are adept at getting quick reloads with it, or that your character has a sizeable reload speed bonus (Crash, Bastille, Wildcat). The sniper rifle is able to pierce doors, allowing you to thin out the herd before engaging it. Sniper rounds penetrate 1 enemy, allowing you to hit 2 targets at once. Rail rifle rounds travel until they hit a wall, damaging all the swarm in their path.Flamer
A powerful crowd control weapon in skilled hands, or a team kill disaster waiting to happen. Its secondary fire is a fire extinguisher, use it if you've made an oopsie, or if you're faced with a wall of flame. Use short puffs to conserve fuel and avoid settings your teammates ablaze; its damage to team members (And, indeed, the swarm) is so little that it is perfectly fine to send a few puffs through a teammates if they are being swarmed, provided you don't overdo it. It is, however, not a kill weapon, so avoid bringing too many of these, or you will simply be crushed by a swarm of burning drones. Be wary of using it too liberally if you have hardcore friendly fire enabled, as it will be more prone to set teammates on fire.Chainsaw
The chainsaw is wonderful for opening doors and breaking rocks in a hurry, if your character has a good melee damage bonus (Vegas, Jaeger). When using it, avoid moving away from a nearby drone - it will lunge and hit you, instead go toward the enemy to kill it. Try to avoid using it as primary weapon, as doing so will cause you to constantly run into your teammates' lines of fire, resulting in decreased squad performances due to them having to afford you special attention. Chainsawing a tesla-stunned shieldbug or mortarbug is the most efficient way to deal with these enemies. If you are short a person, a proficient chainsawer (likely playing Vegas) can hold the front or back sufficiently - it works best solo or backed by a tesla cannon.Grenade launcher
The last weapon unlocked in the game, the grenade launcher is a weapon of massive devastations, which it will visit indiscriminately upon friend and foe. Very useful against small and medium-sized aliens, killing most in 1 shot. Grenades have a large area of effect, so care should be taken when attacking enemies close to you or your teammates. With some practice you may be able to dispatch nearby enemies by shooting grenades to the side so that the enemy is in the blast radius, but you aren't. Very ammo-efficient, refilling its 3 clips with just 20% of an ammo satchel. Not a team weapon and incredibly dangerous in untrained hands, most likely should be avoided if you want the satisfaction of completing a mission as a team - it's not a lot of fun to run through a mission if somebody has killed all the aliens on their own.Sentries
The sentries are useful for defending an area. It is a good idea to deploy one before starting a hack of opening an unrealistically slow door. The regular and freeze sentries are the most efficient, while the flame sentry is merely adequate. The grenade sentry is a disaster, avoid it at all costs. Sentries don't care about friendly fire and normally don't do any damage to friendlies (Flame and explosive sentry exluded, these ♥♥♥♥♥♥♥s will kill you given the slightest opportunity), but if you have hardcore friendly fire enabled, they become a significant menace if you stroll into their line of fire.
Medic equipmentHeal beacon
Heals teammates within a small radius when deployed. Requires injured marines to remain close to it, which can be dangerous and inconvenient. Requires a full charge to heal the smallest scrape. Inferior in almost every way to the medigun. Its redeeming qualities are that multiple beacons can be deployed to increase healing speed, and that the medic is free to use their weapon after deploying it.Medical gun
Can be used on the move, though it slows down the medic to walk speed. Healing continues for a short time after the gun stops "firing", avoid healing a marine to full health, instead allowing the overheal to bring them to top health.