Secondary Fire

Have you ever felt as though your gun just doesn't have enough kick? Tired of the same old bullet-spewing? Well, have we got the solution for you!

Secondary Fire!

That's right, just add a second trigger, or the right mouse button, and have it trigger any number of special attacks that need at most be tangentially related to the primary fire mode! Sometimes this is handled as a fire mode toggle, changing what the main fire button does, but is functionally the same as a separate trigger. It gives the player a "two guns for the price of one" effect. It also eases the job of the mappers to an extent, since finding a new weapon usually requires a lot of design aspects to make it feel like an event to remember. Cutting these events in half gives more time to make the times you do get a weapon more exciting. These secondary fire modes can be roughly divided into several categories:

Burst or Rapid fire: Usually found on pistols, sometimes on rifles, this allows for a faster, but less accurate series of shots, generally intended to be used at short range or during more intense firefights where precision is unneeded. A variant of this often appears in games featuring a double-barreled shotgun, firing both barrels at once.

Grenade Launchers: Most common on assault rifles, but can appear on any gun, these launch explosive shots that usually can damage the player as well, but take things down fast. It may use the gun's standard ammo, but more often has its own ammo supply which may be hard to come by.

Melee Attack: Often used in place of a default hand-to-hand weapon, a secondary fire might involve hitting the opponent over the head with the gun, which may have blades or spikes specifically for that purpose. Same goes for rifle butt strike. See also Pistol-Whipping.
 * Melee Block: In games with dedicated melee weapons, the alt-fire may allow you block other people using melee weapons, possibly also countering. This is most often applied to swords.

Zoom: Almost exclusively on sniping weapons - allows use of a scope to make accurate shots over a range. Usually this is useless at short range because it obscures your view and/or slows down the speed of the cursor so you can't easily track nearby targets. This includes the iron sight modes common in the more realistic shooters.

Deploy: Usually appears on machineguns and other heavy weapons - sets the gun on bipod/tripod and usually makes the soldier immobile until "drop gun" command or un-deployment. Sometimes deployment or dropping leaves the weapon in "turret" mode that can be readily used by someone else. Switching back and forth takes time. The gun may or may not be useable in un-deployed mode at all, and if it is, accuracy when fired from hip will not allow to reliably hit a barn beyond point-blank range.

Charged Attack: This is the province of the Energy Weapon, usually allowing a high damage shot that takes time to charge up. You may or may not be able to hold the shot safely, or the gun may explode if you try to charge it too long, but the results are usually a One-Hit Kill on anything you fire it at. Often this is activated by holding in the primary trigger rather than using the secondary.

Spinning Barrels: If your game has a Gatling gun among your arsenal, it may take time to spin the barrels up to firing speed. Many games feature a secondary fire that spins the barrels without firing, so that when you do hit the fire button, it starts shooting immediately. This feature often causes the gun to overheat faster as a drawback.

Related But Different Secondary Fire: Weapon which has secondary fire which uses same type of ammo as the primary fire, but the projectile itself is different. For an example, primary fire Shock Rifle in the Unreal series is a hitscan fire but the secondary fire shoots a plasma ball.

Completely Unrelated Secondary Fire: Weapon where secondary fire uses different type of ammo and its nature is very different, too. Painkiller, primarily. This is for weapons that don't fit any other category, where the secondary fire has little to do with the primary, such as a shotgun with a freeze ray attached.

This is also Truth in Television, as most modern assault rifles have at least a fire selector for automatic, semi-automatic, burst fire, and similar modes, as well as underslung grenade launchers and shotgun attachments, and also the bayonet, a knife attached to the end of the rifle as a melee weapon.

See also Swiss Army Weapon. Not to be confused with Friendly Fire

Fire

 * Several guns in the Fallout series have selectable rapid fire modes. In Fallout Tactics, the double-barreled shotgun can fire either one or both barrels at once.
 * Most guns in the X-COM games can switch between single-shot and rapid fire. Or rather, Aimed Shot (slow but accurate), Snap Shot (fast but less accurate), and Auto Shot (woefully inaccurate individually but you get a burst of three).
 * Gears of War 2's Hammerburst rifle was automatic and had no recoil, but fired slowly. Pressing the trigger continuously as fast as possible would make it fire much faster, but give it a lot of recoil.
 * The Hive Hand in Half Life.
 * Strangely enough, the Glock 17 as well. It's actually a Glock 18 with a 17's model; the 18 was select fire.
 * Perfect Dark had a secondary fire setting for every weapon. For example, the Magsec 4 could either fire semi-auto or 3 round burst in exchange for worse accuracy than the standard Falcon 2.
 * Golden Eye 1997 had selective fire on most of its automatics. Tapping the trigger button would fire a single shot, pressing it once would fire a three-round burst, and holding it would engage fully automatic fire.
 * The Enforcer and Minigun in Unreal Tournament both have a secondary fire mode that decreases accuracy but makes the gun fire much faster.
 * Some guns in the original Call of Duty had the option to switch between full-auto and semi-auto (or between "full auto" and "slow auto" for the BAR), though since most people just stuck with full-auto they removed it for the second game. Some developers apparently tried to re-implement it as an attachment in later games, but it has never been used.

Charged Attack

 * The BioRifle in the Unreal series.
 * Mega Man and Mega Man X are perhaps the iconic examples with their Arm Cannons.
 * Similarly, Samus.
 * The Plasma pistol from the Halo games do this, activated by holding the primary trigger.
 * Any ship from R-Type.
 * The pistol in Half Life 2 had a charged attack that caused rapid fire; it was actually a bug, which was removed in Half-Life 2: Deathmatch and, much later, also removed from the original game as part of the Orange Box/Mac port.
 * More true to the trope is the Tau Cannon in the original game- the primary fire shot quick blasts, while the secondary fire could be charged up. When charged, the thing could be used to take down helicopters.
 * The Mauler energy pistol from Perfect Dark would automatically charge up as long as it was set in charge mode. It used five rounds to become fully charged, and reloading would cause the charge to be wasted.
 * All the weapons in Bulletstorm.
 * Oddly enough, the shotgun analouge in Tron 2.0
 * Phoenix Samurai, James Bond Nightfire.
 * The Cow Mangler 5000 can fire a stronger blast that charges itself over a few seconds. It is triggered by the right mouse button, no less. The charged shot takes up the full clip, though, and the charging time is not variable.

Grenade Launchers:

 * Aliens: the marines fire grenades and bullets. Ripley's duct - taped supergun also has a flashlight and flamethrower.
 * In Serious Sam II, secondary fire, with the exception of sniper rifle, throws grenades.
 * GURPS: Ultratech allows you to attach a grenade launching railgun to most two handed weapons. It only gets one shot, but still pretty awesome.
 * The SuperDragon assault rifle from Perfect Dark. Its lesser version, the Dragon, had a unique variant; activating its secondary fire let you throw it on the ground and use it as a proximity mine. Very useful against ammo campers.
 * The SMG in Half Life 2. Unlike the standard grenades, these grenades explode on impact. (They are also rather rare.)
 * Its predecessor in the first game was either an MP5 submachinegun or an M4 assault rifle (depending on whether or not you have the Hi-Def pack) equipped with an M203 'nade launcher.
 * Call of Duty 4: Modern Warfare and its sequels both have grenade launcher attachments to most of the game's assault rifles. Modern Warfare 2 and later also have a similar shotgun attachment.
 * The stakegun in Painkiller.
 * AIMS-20, James Bond Nightfire.

Melee Attack:

 * Although definately not the first game to do this, Halo and its sequels certainly popularized it.
 * In Left 4 Dead, the usual "secondary fire" button is used for melee attacks. However, when holding a healing item in front of a teammate, it allows to heal him instead of yourself. This can lead to amusement when the healer doesn't have the teammate correctly centred in their view, and appears to be brutally clubbing them with a first aid kit.
 * In Darkwatch, a vampire/western shooter, all weapons have a bladed or piercing end somewhere that can be used as a powerful melee attack.
 * Several pistols in Perfect Dark that didn't have a unique secondary mode would have a Pistol Whip as their secondary. The Tranquilizer had a "Lethal Injection", which was also a melee attack.
 * Tron2.0 has this for the Disc type weapons, as well as the block, which can deflect other discs
 * Timesplitters: Future Perfect has this for most if not all weapons.

Zoom:

 * Any video game that features sniper rifles.
 * The ultimate example has to be the Farsight rifle from Perfect Dark. Not only could you shoot through walls, but the secondary function caused you to automatically zoom in on the the closest target!
 * A nerfed version of the Farsight also appears in Time Splitters: Future Perfect, a Spiritual Successor to Perfect Dark.
 * The left trigger does this for every weapon in Mass Effect
 * A variation in Half Life - secondary fire activated the laser sight for the rocket launcher and, in Opposing Force, the Desert Eagle. This didn't zoom in, but it did let you guide launched missiles and made the Deagle more accurate.
 * The crossbow featured in both games had a zoom effect. The .357 featured a zoom in as well if cheats were enabled.

Spinning Barrels:

 * The Heavy Weapons Guy from the Team Fortress games can spin up his minigun, at the cost of movement speed.
 * Perfect Dark's Reaper can do this, with the addition of blades on the barrels, allowing you to grind things up.
 * Both Time Splitters 2 and Future Perfect had miniguns that had spinning barrels as secondary fire, at the cost of making the gun overheat faster. 2 had it worse, since if you overused this function then it triggered a sound glitch that caused the sounds of the barrel to persist throughout the entire match.
 * The Death Machine from Call of Duty Black Ops is a minigun given to you from Care Packages, and when you try to aim down the sights, it will instead spin the barrels. Same for the mounted miniguns in the Modern Warfare games.

Related but Different Secondary Fire:

 * Half Life 2's shotgun alt-fires both barrels at once. Which is funny, since it's not a double barreled shotgun. On the Real Life SPAS-12 the in-game shotgun is supposed to be, the "second barrel" is in fact the tube magazine.
 * In the same game, hand grenades can be thrown with the primary fire button or tossed underhand with the secondary.
 * The latter function is vital for getting grenades through narrow holes at close range, such as during the sequence where you take down the Suppressor.
 * The pheropod's secondary effect is "come here, antlions". As opposed to "go over there, antlions", which is what you'll do far more often.
 * In Unreal II the Awakening, the standard assault rifle's alt-fire mode uses the primary ammo to launch a cluster of shards that initially acts like a shotgun slug if it hits an enemy. If the slug hits something that isn't an enemy (like the floor or a wall) then the shards ricochet off on their own.
 * Similarly, the altfire for the aptly named Hydra grenade launcher didn't do anything except cycle ammo. However, if you held the primary fire down before launching, it'd engage a time delay fuse for the grenades rather than a standard impact fuse. Then there's the flamethrower, which spewed out unstable, unlit fuel so you could make traps - though it'd spontaneously combust anyway if left for too long.
 * The Flak Cannon from the Tournament side of the franchise, meanwhile, launched fragmented grenade shrapnel as its primary fire, with secondary launching the whole grenade for a more powerful attack.
 * In many games where you control tanks, noticeably in Mass Effect and Halo one button will use a machine gun turret mounted on the tank, while the other will fire the tank's artillery canon.
 * The Pyro's Flamethrower in Team Fortress 2 has a secondary fire that shoots a burst of compressed gas to push back people, extinguish burning teammates and deflect projectiles: it uses the same ammo counter as the flamethrower's flames, costing 20 ammo per burst.
 * A truly bizarre example is found in the original Red Faction in the form of the sub-machine gun, which is effectively two entirely separate automatic weapons bolted together. Primary fire uses the same rounds as the pistol but at a much higher rate, whilst the secondary trigger fires the same rounds as the assault rifle, only with half the magazine size and not as accurately. Even the bots in multiplayer appeared to think the latter function was completely pointless.
 * The same game gives us a number of less memorable examples. The assault rifle and shotgun both have the option of burst or fully automatic fire (the shotgun works a bit like the option for twin-linked or alternating fire for certain weapons in Descent), the rocket launcher can be either dumb-fired or homing, and the grenade can be set to either a four-second timer or impact fusing. Another slightly odd one is the flamethrower, whose fuel tank can be unscrewed and thrown to act like a Molotov Cocktail when it hits. Even for a Mega Corporation whose lousy safety record is actually a plot point, that makes very little sense. It also follows the convention for vehicles which is discussed above.
 * Perfect Dark has Double Blast for the shotgun (single-barrelled, but fires twice), the Callisto NTG's High-Impact Shells (more powerful but with a slower firing rate) as well as as proximity and timed functions for several other weapons.

Completely Unrelated Secondary Fire:

 * Perfect Dark has unrelated secondary modes on several guns, with the Laptop Gun's sentry mode as one of the most memorable. The Phoenix fires two completely different types of shot using the same ammo (laser vs. explosives).
 * Team Fortress 2 usually uses the secondary fire as a complement to the weapon (zoom the sniper rifle, detonate remote mines, spin up the minigun, etc.), but a couple are used to activate special items the player has equipped: the cloaking device for the Spy, and the Chargin' Targe for the Demoman if he's holding it.
 * Painkiller plays this trope to the hilt, and then a bit farther: each weapon has two modes of fire, each drawing from a unique ammunition pool (exception: the rocket launcher and grenade launcher both draw from the same pool.) Additionally, it gives some weapons a third mode that can be used by combining the existing two modes -- for example, if you use the Painkiller's primary fire (spinning blades) then hit the secondary fire (launching the blades) you get spinning blades flying through the air. And it is awesome.
 * The Overwatch rifle in Half-Life 2, which alt-fires disintegraty energy ball thingies. Could be vaguely considered a grenade due to its one-hit kill nature.
 * Warhammer 40k has this with the Space Marines Combi-weapon which combines the standard bolter with either a flamer, plasma gun or a meltagun. Though these extra weapons only have one shot (which the player can use whenever he wants) and will for the rest of the game count as an ordinary bolter.

Uncategorized/other:

 * The Gravity Gun in Half-Life 2 onward doesn't have a primary and secondary fire in the strictest sense -- you need both of them more or less equally -- but assigns throwing things to the primary fire button and pulling them in to the secondary.
 * Some Half Life mods followed the trope as well.
 * The Specialists was a mod that focused on stylish, action-movie style gameplay. Some guns had scopes. With guns akimbo, your secondary fire button shot the other gun. Then, there were some secondary fire modes that just changed how you held the gun, to no benefit other than the obvious.
 * Most weapons in Day of Defeat provide more than one mode. Rifles have either bayonnet or butt strike; Sniper rifles zoom; machineguns, BAR and FG 42 deploy bipods.
 * Eternal Darkness features an OICW in the second to last level which fits types 1 and 2. The rifle portion can be switched between semi-auto, burst and fully automatic fire, and it is also underslung on a semi-automatic grenade launcher.
 * In Diamonds Are Forever, James Bond used his Walther PPK to attach a cable to a building from a distance.
 * Zorg's gun in The Fifth Element. This had standard bullets, rockets, net launchers, liquid nitrogen, flamethrowers... and the little red button on the bottom of the gun.
 * Bioshock effectively goes the mode-selector route by giving guns different ammo options, some with widely varying effects.
 * Best example: the chemical thrower. A weapon that shoots liquid nitrogen, napalm, and electrified goo? DO WANT.
 * Dead Space handles it well with every gun having two firing options, including explosive grenades and room-clearing circular attacks.
 * Blood. The secondary fire options for various weapons included: starburst incendiary flares for the flare gun, a shot from both barrels at once for the sawed-off shotgun, a strafing fire for the Tommy gun, tossing the flammable spray cans, the ball of lighting for the Tesla cannon, and ripping the head off a Voodoo doll (a very powerful attack, but renders the doll useless).
 * Later patches and/or expansion packs also added a devastating attack for the Napalm Launcher ans the ability to drop the Soul Leech on the ground so it could act as a sentry gun. Blood was also one of the first shooters that featured secondary fire.
 * Blood 2 continued on the fine tradition, and even included and alternate attack for the melee weapon; a slow but powerful reverse-grip slash.
 * Star Wars: Dark Forces Saga was one of the first FPSes to have this. Every weapon had a secondary fire mode, including rapid fire modes, cluster-firing modes for weapons with multiple barrels, alternate detonation options for grenades/mines, and a rocket-launcher option for the Dark Trooper weapon.
 * Naturally, every weapon save lightsabers and generic explosives from the Jedi Knight games also had a secondary fire function that fulfilled one of the types above.
 * The Wookiee crossbow in particular included a Charged Attack with its primary firing mode, and its secondary fire was a projectile that could rebound off of walls.
 * Perhaps lazy programming or a lampshade hanging, in Jedi Academy, toggling a console command changed Force Lightning into a flamethrower.
 * The lightsaber actually did get a secondary fire in Jedi Knight II: the saber throw power.
 * Every weapon in the Unreal series. This also extends to vehicles and mod weapons.
 * A rare RTS example: Command & Conquer Red Alert 2, which had a love affair with letting units deploy to unleash a secondary, related attack (usually requiring them to remain stationary). For example, the Desolator unit's normal attack was a radiation gun capable of wiping out individual infantry, but it could also deploy to poison its entire surroundings and kill many more infantry and even other ground units like tanks.
 * Red Alert 3 takes this even further; almost every unit has a secondary mode. For the Japanese units, this may even be as drastic as transforming into an aircraft and back again.
 * Another RTS example is Ground Control II, where every single unit (except for the deployable turrets and radars) had two modes. Those varied from switching between a tank's machine gun and cannon, having infantry kneel down and pull out anti-tank weapons, disabling a unit's weapons to boost speed or health regeneration, to deploying a tank's side armor, making it vulnerable in the sides and rear but almost impervious in the front, and giving cover to nearby vehicles. This Troper is sure he could find even more interesting examples if he tried.
 * Marathon was perhaps the first to do this, with dual-wielding pistols/shotguns, a fusion pistol (with the option of charging up for more powerful shots or autofire), an assault rifle/grenade launcher, and a rapid-fire alien weapon that could fire straight ahead, at 45 degree angles, or both at the same time.
 * Narrowly beaten by the original System Shock, which featured multiple ammo types and sliders to select the power output of energy weapons.
 * System Shock 2 - the only weapons that didn't have multiple firing modes and/or ammo were the melee ones. Most of the modes were a choice between more power/accuracy or More Dakka.
 * Clive Barker's Jericho has Black's sniper rifle, which fires grenades on alt fire instead of firing a second weapon as it does with everyone else.
 * Gunman Chronicles. Every gun had a whole menu to configure it. From memory...
 * The pistol could be switched between laser beam, rapidfire energy orb, high-power energy orb, and sniper laser.
 * The shotgun could adjust the number of shells per shot and spread.
 * The machinegun could be switched between semiauto rifle and rotary machinegun modes.
 * The rocket launcher... oh god.
 * The payload can be explosive or cluster.
 * The detonation can be on impact, with or without timer, on proximity, or on tripping a laser beam after impaling the warhead in a wall.
 * The rockets can be launched dumb, spiralling, guided or homing
 * The grenades are cannibalised rockets, so they have most of the above settings.
 * The toxic gun can fire a variable mix of acid (which damages organic targets), base (which damages mechanical targets) and neutral (which keeps a mixture of the above two from exploding in your face).
 * It may not be an FPS, but Valkyria Chronicles gave some of its classes a secondary fire. Scouts could be upgraded to have grenade launchers attached to their rifles (given that they have hand grenades anyway, this is mostly a range upgrade) and Stormtroopers could be upgraded to have flame throwers attached to their machine guns.
 * The Gears of War games have a gun with a fucking chainsaw attached to it.
 * A rare cinematic example: The .45 blaster used by Deckard in Blade Runner is hypothesised to be a two-barrelled beast, the lower barrel being a standard pistol, and the upper barrel firing a special, more powerful round. The fact it has two triggers (and is therefore twice as awesome) would support this.
 * Every weapon in Flying Heroes has a secondary fire. These are always at least somewhat related to the weapon's primary fire -- for instance, the secondary fire for the tier 5 weapons (which ordinarily fire homing rockets) shoots a manually-guided rocket. The secondary fire is the same for most weapon tiers of each clan, but certain clans get specialized secondary fires that play to the clan's theme -- for instance, while the secondary fire for other clans' tier 1 weapons is just a more powerful version of the primary attack, the Magion's tier 1 can sap mana from nearby enemies.
 * Jak's Morph Gun and Gunstaff can be used to smack people around and combining them with a jumping spin-kick can increase their rate of fire.
 * Dystopia contains all versions except for an unrelated secondary:
 * The Laser Rifle, MK 808, and Ion Cannon all zoom in.
 * The Assault Rifle zooms and goes to burst mode.
 * The Bolt Gun and Grenade Launcher detonate their respective projectiles.
 * The Tesla Rifle, instead of shooting lightning like the primary fire, charges and slings ball lightning.
 * The Basilisk (autoshotgun BFG) shoots a grenade.
 * The Rocket Launcher shoots in Fly-by-Wire mode.
 * The Smartlock Pistols shoot a tracer round and lock on.
 * The Shotgun fires two barrels.
 * The Minigun spins up.
 * The Katana blocks incoming Katanas.
 * The Resistance series loves this trope. Literally every single weapon has a secondary fire, which fall into all the categories above.
 * As does the earlier Star Trek Elite Force series, with most of the guns falling into the related-but-different format, but the second game includes at least one example from every category.
 * Smokin' Guns secondary attack gives rapid fire secondary mode to revolvers, as single-action with two hands (i.e. very quickly cocking the hammer with left palm) rather than normal double-action, for two revolvers triggers simply use left or right gun; for double-barreled shotguns it's a double shot; for knives it toggles melee and throwing modes; for dynamite and molotov cocktail  ignites fuse; for Sharpe rifle zooms (if you purchased a scope); Gatling gun is deployed on tripod and collapsed back to portable form (it cannot be fired from hands, obviously).
 * UFO Alien Invasion has traditional X-Com Snap/Aimed/Burst choice for most conventional guns, and just Snap/Aimed for sniper rifles and basic handgun. It used to (before v2.5) have Snap/Burst on riot shotguns with flechettes and Aimed for slugs. Some weapons also have "full-auto" mode. Machineguns have Burst/Full Auto/Full Auto Sweep, flamethrower have   much the same options named "Candlelight", "Inferno" and "Inferno Sweep". Grenade launcher used to have 6 ("Airburst" and "Timed" settings with 3 basic modes each), only 4 from v2.5 (Snap/Aimed x Impact/Timer). Hand grenades allow "Lob" and "Roll" options (roll usually is more precise - on smooth floor - but an indirect attack is the main use for grenades to begin with). Knives allow to Stab or Throw. Researched weapons have various modes, sometimes including supercharged, but mostly subsets of basic four.
 * The Dual Pistols powerset in City of Heroes allowed you to change your ammunition type on the fly, between "normal", "cryo", "pyro" and "toxic" bullets; "normal" bullets were more immediately lethal, the others inflicted a lower initial damage and then applied DoT damage of their type to the target.