Louis: We made it... I can't believe we made it! Bill: Son, we just crossed the street. Let's not throw a party 'til we're out of the city.
A Co-Op MultiplayerFirst-Person Shooter developed by Valve and proclaimed by its advertising as "the Zombie Apocalypse you can play with your friends." Left 4 Dead reduces the zombie genre to its absolute basics: You are one of a Ragtag Quartet of Misfits caught in the middle of the outbreak of a deadly virus that's turning people into bloodthirsty mutants. Your objective is to make your way from safe house to safe house through an area infested with these murderous creatures, and finally reach a pickup point from which to summon the cavalry to spirit you to safety.Of course, this won't be easy. You have your three pals, and due to the Drop-In-Drop-Out Multiplayer nature of the game, there are fairly-competent AI bots standing by for when you don't have allied players. And don't worry about them hogging the kills: there are plenty of infected to go around. There could be a herd of thirty zombies, or just one extremely powerful mutant zombie, waiting around the next corner. The game's "AI Director" is watching your progress and planning your next sudden encounter; play the same campaign five times and each time will be a different experience. The director drops health packs less often than you need it and spawns a horde of zombies whenever he's bored. Which is all the time.''Almost as addictive as the Campaign mode is Versus mode, in which eight players, trading off between rounds, control either the Survivors or the dangerous Special infected: the long-tongued Smoker, the lightning-quick Hunter, the nauseous (and explosive) Boomer, and the Tank. In the sequel, the Self-explanatory Charger, the acid-puking Spitter, and the body-clinging Jockey are also available to play as. (There's another type of Special infected — the Witch, who doesn't react well to flashlights and loud noise — but like the Horde she's not actually a playable character.) The goal of Versus is nominally to make it to the next safe room, but nine times out of ten, you won't. The goal is to make it farther than the other team.The expansion pack takes it further with the ironically-titled Survival Mode: "survival" is pretty much the last thing you'll be doing. The question is how long you and your friends can hold out against an all-out Infected onslaught before you all die.The game also received massive critical acclaim for both its Myth Arc style narrative - the parts of the story they don't tell you, as well as the interactions between the survivors - and for its emergent narrative, in which different aspects of gameplay combined with elements of randomness mean that every single time you play a new, funny story emerges.Please take a look at the character sheet to learn more about the characters and the Shout-Out page for countless pop culture references.Due to the number of examples, they have been divided into categories.Not to be confused with the trope of Left for Dead. See also Resident Evil Outbreak.Followed by Left 4 Dead 2.
"October 2nd Johnny killed 12 Infected with his bare hands"
"October 4th Johnny was killed by friendly fire"
Bilingual Bonus: A piece of safe room graffiti in The Sacrifice is in Japanese - Louis gives the translation, but only the English half. Fluent speakers alone would be able to read aloud the characters he translates.
Bittersweet Ending: The final part of the comic shows Bill jumping off the bridge to restart the generator so the bridge can be fully raised. He gets ambushed by three Tanks and gets killed, but the survivors were able to outlast the horde and take the boat to the Florida Keys to spend the rest of their lives in, thanks to Bill's Heroic Sacrifice.
Credits Gag: The end of each campaign has a credits roll which actually consist of statistics for the players (most infected killed, most headshots, etc.), ending with a disclaimer reading, "[X number of] zombies were harmed in the making of this film."
Cryptic Background Reference: The only parts of the story that are completely laid out for you are from the single 4-chapter comic ("The Sacrifice"), and the short character bios that each of the Survivors get (neither of which are found in-game). The rest of the plot that's given to you will only be through random (often campaign-specific) character dialogue, about 99% of which isn't even guaranteed to trigger (usually requiring multiple play-throughs if you want to catch everything), or occasionally from significant pieces of the map, but most of all from the writings on the walls of different saferooms (and occasionally elsewhere) of other people who have passed through that area, describing bits of their experiences as messages to others, agreement or disagreement with what the military is/was doing, just how bad CEDA failed, how fast somebody changes into a zombie after being infected, and so forth, but not even those people are in 100% consensus about whatever's been going on, and nobody really has any idea what evenstartedthe whole thing.
Dungeon Bypass: Guarding the doors and windows is all well and good, but more often than not the horde just crashes through a wall.
DVD Commentary: Like all Valve games, both Left 4 Dead games have a commentary mode, where you can play a campaign that contain commentary nodes which will play commentary audio from the developers. You're locked in Easy difficulty and zombies will ignore you. Naturally, you can't earn achievements this way.
Elevator Action Sequence: The fourth level of No Mercy requires holding off the horde while waiting for the elevator. Subverted on the elevator ride itself; any first time player will constantly give the missing elevator panel nervous glances.
The panel is intact in the sequel's port, to counter Spitters getting a cheap shot.
Escape Convenient Boat: Quite a few. One of them actually kicks them out, though it's only referenced in dialog.
Everybody's Dead, Dave: The only non-zombies you hear from in the game are the playable survivors, the (sometimes) unseen pilots and drivers who rescue you at the end of each campaign, the occasional psycho/weirdo, and occasional gunfire off in the distance.
Excuse Plot: It's basically "You wake up one day, everybody except you and 3 other misfits with eccentric personality quirks are zombies. Try not to get killed".
Hollywood Darkness: Valve uses a fog effect in some areas to mimic the Hollywood technique of "smoking the set", which conventionally uses a fog machine to help create atmosphere in "dark" areas. The fog catches the little light available, which makes everything slightly brighter, and allows viewers and players to see the silhouettes in the distance when they would otherwise be indistinguishable against the dark background.
Idle Animation: The infected alternate between leaning on the wall, sitting in despair, barfing up their guts (literally) and killing one another. The survivors alternate between stretching, wiping their faces, or rubbing their noses.
Incendiary Exponent: Every Special Infected can attack you whilst on fire. Hunters will actually do more damage while aflame, and tanks become faster.
In Memoriam: Played with to humorous effect: players who do not live through a campaign's finale have the "credits" dedicated to them.
The Immune: The main reason why they survived all the shit hurled at them is that they're immune. (At the end of Left for Dead 2 the military forces they have contacted by radio refer to them as 'carriers' which implied that while they themselves are immune, they may infect normal humans.
It's Quiet... Too Quiet: An area is usually only clear of zombies after something big has happened... Or about to happen.
Louis explains this well in the comic:
Zombies are like... piranhas. They ain't too choosy about who they attack, you know? [...] Point bein', you jump into a lake fulla piranhas and you ain't gettin' attacked? Means there's a shark around.
Militaries Are Useless: In the comic The Sacrifice, the soldiers are quite bad at fighting zombies. If three civilians and a Vietnam veteran can kill hundreds of infected with hand-made weapons in the worst possible places (airport, hospital, church), do you think that trained soldiers in a base with twenty feet high walls, barbed wires, artillery, choke points and choppers can do the same ? Of course they can't, they're soldiers.
Justified in that they aren't immune, and so probably wouldn't have as much first-hand, close-up experience dealing with the infected as four people who fought through what was apparently the most populated infected zones there was.
Monster Closet: While the closets are not hidden, several contain absolutely nothing except respawned survivors. However, sometimes a Horde may spawn in it.
Also, some walls are fragile and allow zombies to burst through them.
Since the AI Director chooses which closets are used, exploring players will find empty dead ends that could have been monster closets.
Hordes of 30 zombies spawning out of a closet is pretty much one of the main game mechanics.
At least in the spirit of this trope, though, as you play Left 4 Dead or Left 4 Dead 2, you will encounter plenty of zombie configurations that will make you stop and ask, "How the hell did this happen? How did these guys get here? Why did they stay?"
It can also lead to unintentional hilarity when a witch spawns in a closet. Open door, toss in molotov, close door, wait for the screaming to stop. Repeat as needed.
As the Versus game mode is Player Versus Player, it isn't unheard-of for particularly sneaky or particularly evil Special Infected players to take advantage of small, ignored closets by sitting and waiting until Survivors pass by...or coming up behind them from what they thought was a safe zone.
Musical Spoiler: Musical warning is given for when a horde appears, a tank appears, or when a witch is nearby. It also plays softly whenever any special infected are nearby, making those who know each one's theme music able to know one's nearby even without hearing them or seeing them.
Near Victory Fanfare: "Skin of our Teeth", a fast-paced, intense tune that plays when the rescue vehicle arrives.
The Nicknamer: Francis has a tendency to call his team by pet names on occasion, such as calling Louis "Louie." He'll also call the Hunter cowardly names like "little wussy" and "sweatshirt-wearing sissy."
Night of the Living Mooks: The game pretty much shuffles the Horde's character models at random. The sequel give so much variety of appearances for individual parts of the zombie that the chances of seeing the exact same zombie twice is maybe 1:1000.
Non-Fatal Explosions: Zigzagged; while explosions from grenade launchers, pipe bombs, propane/oxygen tanks and barrels will deal lethal damage to any infected within range, they'll hurt survivors for maybe 5-10 damage at most on Expert.
Not Using the Z Word: Played straight and averted. The survivors call them zombies, but subtitles consistently refer to them as "infected" regardless of the dialogue. The military is fine using the term "walking dead", which would be abbreviated as "WD" and then transliterated as "Whiskey Deltas".
Oh, Crap: The usual reaction the player characters have when a Tank appears.
Stand Alone Episode: All of the campaigns in the first game start with the discovery of an evacuation point and end with the survivors successfully escaping. The developers originally planned to have the campaigns lead in to one another, after the survivors escape but have their escape method fail somehow, but then found that it was too depressing to succeed only to learn how that you'd ultimately failed. Averted in the second game, where the campaigns lead directly into each other. In addition, Crash Course ties together No Mercy and Death Toll, and The Sacrifice comic confirms that all the campaigns from the first game are tied to one another (and, of course, tie into... well, The Sacrifice and The Passing.)
Stupidity Is the Only Option: In Death Toll, you must lower the sewer bridge to get across, causing an alarm and a horde, and you must lower the forklift, causing it to noisily smash some glass and attract a horde. And in the ported version of Dead Air, you must walk through the metal detector in the penultimate stage, setting it off and triggering, you guessed it, a horde.
Suspiciously Apropos Music: In "The Passing", you can play a song about leaving someone (by the Midnight Riders) near a Witch who was infected at a wedding.
Terrified of Germs: Averted, the survivors don't mind being covered in zombie guts. Or fishing pills out of urinals.
Nick plays it straight.
"A little hand sanitizer and we wouldn't be in this mess."
"A germ just wiped out the world."
The Smurfette Principle: Due to the genetic nature of immunity, men have a 3:1 chance of being immune compared to women, which is why there is only one girl in both sets of survivors. Assuming humanity survives this Infection, expect Gender Rarity Value to come into play.
Averted in the Arcade Port. There are two guys (Yusuke and Blake) and two girls (Hirose and Sara)
The Tetris Effect: Play the game for a good hour or so. Close your eyes. See the zombie horde rushing towards you?
Token Minority: Louis in the first game. Averted in the second game with Coach and Rochelle.
The second game takes place in the American South (starting in Georgia and ending in Louisiana) where there are a larger number of Black Americans.
Typhoid Mary: All of the playable survivors are asymptomatic carriers for the virus.
The Unintelligible: The Charger is clearly saying something, but no one can really agree on what it is.
Underestimating Badassery: Implied. The military takes Bill and Zoey — an old man and a young woman — out of the cell (rather than Louis and Francis) to be examined by the doctor. The doctor's bodyguard pokes them with his gun one too many times.
Wham Episode: In "The Passing", Bill is dead. You get to watch him die in "The Sacrifice". You don't specifically have to sacrifice Bill, but you do have to sacrifice someone.
What Happened to the Mouse?: The loose ends of the people that rescued the L4D1 survivors are tied up in the Sacrifice comic, they all turn or can't stand the survivors, L4D2 shows or explains what happens to all in the next campaign.
Artistic License - Engineering: Specifically Architectural Engineering; some of the maps feature buildings with impractical or outright impossible layouts for normal use. The offices in Death Toll's Riverside (the ones immediately before the street crescendo event) have no interior doors in them. The players enter and exit through a balcony on either side, so how would the office workers normally enter?
Artistic License - Law: The obligatory scoped weapon is named the "Hunting Rifle". In Pennsylvania, where the game takes place, hunting with a semi-auto is illegal.
Bag of Spilling: The intro cinematic shows all the survivors using guns that they don't start with. But during that intro, they either drop them, run out of ammo, or are disarmed, and so when the game opens they're just toting pistols. Additionally, this happens at the opening of each campaign as well.
Character Filibuster: The Crash Course campaign features a safe room with a wall covered in a massivePurple Prose poem...And equally-classy replies to it such as "QQ" and "Cool story, bro!"
Darker and Edgier: The Sacrifice comic zigzags between this and more snarks per mile than the games.
Deliberately Monochrome: After being downed and revived twice, you see the entire world in black and white, complete with blurry peripheral vision and red item highlights. If you're not healed, you will die. The developers included this because playtesters were frustrated when inexperienced players were repeatedly going down and delaying the group.
Dirty Business: In order to halt the spread of the infection and save what ever non-infected people they can, the military in The Big Easy made it their policy to gun down carriers (people who don't turn but can spread The Virus) by the hundreds, maybe thousands. Whether this makes them Anti-Hero or Knights Templar is open to debate.
Follow the Leader: High Voltage Software's The Grinder looked to several people like "Left 4 Dead Wii" upon its first announcement. It's still an FPS on the Wii, but the Xbox 360 and PS3 versions have changed formats to a top-down shooter, making it more like a Spiritual Successor for High Voltage's own Hunter The Reckoning.
PAYDAY: The Heist is basically "Left 4 Dead as a crime simulator" - which Valve and Overkill have run with, going so far as to make a mission for PAYDAY actually set in Mercy Hospital.
Game Mod: The Mutation game modes that rotate every second week.
Left 4 Dead in fact originated as a special game setup for Counter-Strike (bots with knives only), which itself originated as a mod for Half-Life.
Griefer: Being a team based game, it is extremely easy to grief other players. Even if the griefer gets kicked, they can just join a new game and do it again to others. This also results in Heel-Face Turn because you never know who will be the first to shoot you dead when it is time to escape.
The mutation, Room for One, is all about griefing your team when the rescue arrives since only one survivor is allowed to escape instead of the whole team.
The griefing problem has been eased somewhat by the 2011 holiday patch that allows players to block a griefer from joining any of their games.
Leeroy Jenkins: Mostly applies to newbies who keep making common mistakes, such as running ahead of everyone (which usually gets them killed and are too far away to be saved in time), angering a Witch without having the right gun for it (only shotguns can kill her instantly with a well placed shot connecting all pellets, and even then, only a headshot will work on higher difficulty levels), or flinging Molotovs like a hot potato and setting other players on fire from it.
Oh, there's more. See the trope page itself for the huge list.
Lighter and Fluffier: Alexandria Neonakis' adorable cartoony designs for the Special Infected, which appear on the licensed Christmas cards, previous Valve Store site headers, and even spawned a series of plushies that make the various Infected's signature noises when squeezed. So far, they've released Boomer, Hunter, and Tank, although a prototype of a Jockey hat is floating around online somewhere.
The Millstone: They show up a lot more than in most online games (or maybe the focus on teamwork just makes them a lot more obvious).
Poor Communication Kills: This will literally be your game ender online if you or the rest of your team fail to talk or at least call for help if being pinned by the infected, especially in Realism and Realism Versus modes where you can't spot each other with glows anymore. Lots of games have been lost due to people simply not speaking up.
Serious Business: Handfuls of people take the game very seriously and will scream at you or call a vote to get you booted if you do anything they don't like (not the Too Dumb to Live type player mind you). More noticeable in VS mode where people will yell at you for not saving them from the infected quick enough and/or yell at you if you don't do enough damage to survivors or just plain outright miss your attacks. note In fact, in most Versus games, when someone becomes the Tank, all the infected players put all their hopes on the Tank player and expect him or her to to kill the Survivors in one go. What most people don't realize that the Tank alone cannot kill the Survivors unless the players are extremely stupid and the Tank needs support from the other infected. If you're the Tank and get caught on fire or die without killing at least one player, expect most people to call you a fail Tank.
Sliding Scale of Continuity: The game is level 0 (Non-Linear Installments) without DLC. Each level is completely stand alone as far as the game leads you to believe. With the release of the DLC, it jumps to level 3 (Subtle Continuity) as we find out that the survivors ended up transitioning from one area to the next.
The Virus: If you're... unlucky enough, you turn into a constantly crying, always-guilty Witch, an exploding fatass, get Gene Simmon's tongue, become a flying Parkour expert, or turn into the Hulk.
Visual Pun: The boxart is a zombie's left hand holding up four fingers, with the thumb ripped off. Same thing in the game's intro.
In the trailer for The Sacrifice, a common infected who gets hit by a car falls to the ground and only its hand is visible on the camera. Its thumb is missing, and its hand twitches so to appear to be holding up the number two briefly; making reference to the box art for the second game.
Anti-Frustration Features: If you don't aim wisely, you'll find yourself running out of ammo very fast even on the lower difficulties. Luckily for you, the ammunition dumps are infinite if somewhat rare, and you get up to two trusty pistols with infinite ammo that work nicely against pretty much everything except witches and tanks. Furthermore, on sub-Expert difficulties, the Director designs the drops so that you always get what you need to take down whatever he's about to throw at you, giving Genre Savvy players an advance warning for the horde that's about to come.
Artificial Brilliance: The Special Infected are quite smart and are very wary of the presence of the players. Hunters and Boomers will always try to hide around corners or behind thick shrubs so that they can ambush the players. The two may also tag team players if a player is caught by a Smoker. Smokers will attempt to run away if their attack fails and Hunters will escape by repeatedly jumping away if they are shot at from a distance. Tanks can try to avoid fire the player makes, assuming the player sets the fire off too early. While they can be quite stupid at times, it doesn't happen too often.
Hunter and Smokers will occasionally retreat if spotted, and try to get to places that the survivors can't reach easily before attacking.
Artificial Stupidity: Although not too horrible, the Survivor AI has many infamous quirks. This is a great reason to play the game with actual people.
Boomers sometimes hide behind street lights & most zombies sometimes swerve away from their target at the last second to try to break through a door that isn't in the way. They'll also run through fire to get to you.
Aura Vision: Used to find teammates as Survivors and used by Infected to find Survivors health and location.
Bad Boss: The Director in Versus mode. Between showering the survivors with first aid kits and often not bothering to send a horde after a boomer attack, it clearly hates the Infected players even more than the Survivors.
Averted with the survivors. When seriously injured, you run slower and jump lower. After taking pain pills, or having just been revived by a teammate, your health is constantly dropping, and at 1 HP you slow to a crawl. If your health gets taken all the way out and you're not on your "last down", you drop to the ground, only able to use pistols, and slowly bleed out until you die or are revived by an ally.
Justified by the Infected, who obviously no longer have a self-preservation instinct and are extremely aggressive, causing them to come at you with all they've got no matter what happens to them, until one of you is dead.
Damage-Sponge Boss: They're called Tanks for a reason. Four Survivors starting a level have a group total of 400 HP. On Normal difficulty, the Tank has 4,000.
Death Is a Slap on the Wrist: Dying does not mean you are forever gone from the game. You will just respawn in a closet or come back in the next map. Versus mode prevents you from coming back until the next map and dying during a finale on any mode gets you Killed Off for Real.
Death Is Cheap: You can be rescued from a closet in campaign mode or just simply respawn in the saferoom in the next chapter.
Difficulty Spike: The jump from Advanced difficulty to Expert is huge. On Advanced, a common infected will deal 5 points of damage if they hit you in the front whereas they do 2 damage on Normal and 1 on Easy. On Expert, common infected can cause 20 points of damage in the front. Hunters can slice you for up to 40 points of damage, dealing the most damage out of all of the infected on Expert except for the Tank, who can instantly bring you to incapacitation in a single strike. Not to mention that Witches, which previously incapacitated you in one hit as well, now just flat out kill you.
The Sacrifice was a huge bump up from all the other campaigns, mostly due to its finale. Unlike the other finales, the hordes AND the Tanks attack at the same time. And there are three sets rather than two now. And one achievement involves setting off all three at once. And then just when you think you've made your escape, the lift engines stall and you have to sacrifice a survivor to go re-activate the lift. With 3 more tanks and another horde all gunning for him.
The Director Is A Cheating Bastard: Unusual, in that the Director is supposed to be continuously tweaking the challenge of the game up and down based on how well the players are doing. However, on Expert, its moments of mercy are extremely brief.
This goes for the survivor bots too, as they have aimbot-like accuracy, and cannot directly cause friendly fire(being able to literally shoot through others). It works, as a half-decent human player is still more efficient overall (due to other factors like bots not being able to use grenades or any particular strategy beyond shooting things), yet a team isn't completely screwed if a player leaves mid-game.
Under certain conditions, survivor bots will grab items through walls. Players can't, though in "Death Toll" there is at least one stairway you can revive downed teammates through.
Any special infected (other than witches or tanks) can slash you with their claws if you manage to shove them. No "attacking while staggering" animation or anything, blood literally just pulls itself out of your chest.
In co-op and other modes where the special infected are AI-controlled, the specials can spawn inside the safe room at the end of the level, leading to fun times. In versus, where the specials are human-controlled, you cannot spawn in the ending safe room, but you can spawn outside of the safe room and go inside. Playing as a Boomer or a Spitter, you can buy the rest of your teammates time to respawn and make one last attempt at the Survivors.
Exploding Barrels: Gas cans, propane tanks, oxygen tanks, and actual barrels in the Sacrifice campaign.
Falling into the Cockpit: Versus mode, infected team. While a player can run through the campaign mode to build up their survivor skills before going in, infected players have to learn it all on the fly for their randomly assigned characters.
Fetch Quest: Going through waves of infected for some gas.
Friendly Fire Proof: Downplayed with the survivors. They can get shot, how ever it barely hurts them. You can fire a sub-machine gun at them and still have to reload a few times before they're incapacitated. In Versus Mode, the special infected can't hurt each other, but they can hurt the common infected, apart from the Tank, whose habit of accidentally killing team mates can be quite frustrating.
Gang Up on the Human: When playing solo, the special infected seem to favor targeting you over the other survivors.
Genre Savvy: Zoey spent her time in college watching zombie horror movies, so she knew how to survive.
Ironically, ties into Zoey's background: she watched zombie movies with her dad a lot. When he was bit, he had her kill him, as per zombie movie tropes. Turns out... he was immune.
Zigzagged with the military in the Comic. The guards outside Louis and Francis do not fall for Francis' attempt at making them come to the cell and get overpowered. They do however make the mistake of thinking one man with a gun is capable of controlling Zoey and Bill.
Guard: You're trying to get me angry so we'll come in there, and you can over power us and escape, aren't you? Francis: What? No. Okay, fine, yes.
Goomba Stomp: Jumping on a common infected's head is instantly fatal. Doesn't apply to special infected.
Physically being on top of a zombie counts as a stomp, thus an instant kill, which leads to a hilarious moment where you can literally walk over a zombie lying on the ground and kill it from just stepping on it.
If you're on a raised position and zombies are climbing up to you, you can drop down and string two or three Goomba Stomps in a row.
Standing on top of a ladder which zombies are trying to get up will cause them to get stuck at the top. Jumping will then instantly kill all of them.
Gravity Barrier: keeps you away from a zombie breeding ground and to keep you moving along to your safe house.
Griefer: Per GIFT, you're guaranteed to come across them in public matches.
Playing as the infected is basically griefing the survivors as the goal of the game. The griefers are getting their kicks from the game itself most of the time!
Guide Dang It: Medkits restore 80% of the damage you've taken—if you're at 90 Hit Points it will give you 8, and if you're at 1 it will give you 80. As such, there are times when using them is seriously inefficient. The place this is spelled out in the game is nowhere.
Hell Is That Noise: Every single type of Infected has their own distinct sound/musical cues to warn you of their arrival, including a few who will switch from low growls to all-out screams or roars as soon as it has one of the Survivors in its line of sight.
He's Just Hiding: Literally. Whenever one of the guys die, they're found later trapped in locked closets (or respawn in the next saferoom). It was meant to reflect how survivors get rescued in zombie films. invoked
Averted in the final chapter of each campaign after the rescue vehicle has been summoned. Dying means you get Killed Off for Real.
Hitbox Dissonance: Hitboxes for hunters move in front of them when they pounce, which makes them extraordinarily difficult to knock out of the air with even the slightest bit of lag.
Hold the Line: Occurs in all crescendos and finales(except a couple in the Parish) as well as survival mode.
Hyper Awareness: Meta example. The best players exhibit this, being aware of all the directions from which infected could attack and keeping their eyes (and ears) open for incoming specials. Players that turn on subtitles can get alerts for specials before they actually see or hear them. In comparison, the AI bots (as mentioned above) are Lazy Backup with a horrific case of Selective Obliviousness.
Getting hit with Boomer bile turns your screen green and blurry. Not a good thing when that same bile acts as zombie bait.
Invisible Wall: Only the Infected in Versus mode will run into them, and if you get close enough they stop being invisible... instead they become labeled "wrong way!"
It Can Think: The Director is actually a rather well working AI system. Depending on the difficulty, it will decide when to place more zombies to hinder your efforts. On Expert difficulty, it just wants you dead and doesn't pull any punches.
Killer Game Master: The AI director. Particularly on Expert mode, when he stops even pretending he doesn't hate your guts.
Limited Loadout: You can carry one primary weapon from a selection of five, either a single or pair of duel handgun(s) with unlimited ammo, one thrown explosive (either a pipe bomb or a Molotov,) one bottle of pills, and one medkit at a time.
Luck-Based Mission: Depending on where enemies spawn and what types they are, along with what items you find, you can either have a smooth sailing game or a nightmare of just trying to survive.
Muscles Are Meaningless: The Witch is a small girl with relatively thin limbs (apart from the vicious claws)... limbs with which she can knock you down/kill you outright faster than any other Infected. Including the muscle-mountain Tank. Justified, at least in part, by those claws and perhaps by what could be argued as an overactive metabolism - she's clawed most of her own clothes off, can't stand the light of day, and is drawn to the smell of sugar. The Tank's bulk is more weight that his muscles have to overcome (though you don't want to get in the way of his fist once it's moving, and even less in the path of a car he's just flung at you - that can incap the entire team in one swipe), whereas the Witch's constant supercharge and lack of excess weight means she can swing those claws with deceptive range and vicious speed.
My Rules Are Not Your Rules: AI-controlled Survivors occasionally get stuck in the environment, so they simply teleport to the nearest survivors position. AI-controlled infected can spawn anywhere, melee while stumbling, climb things player-controlled infected cannot, and AI-controlled hunters even have a lunge move players cannot perform.
Occasionally averted in Expert and Versus matches when one survivor staying in the safe room with the door closed can be the difference between success or failure.
There are also a few jarring situations in which you have passed a Point of No Return and cannot go back and help your teammates. This just reinforces the original lesson, since you are forced to soldier on short-handed.
Nerf: The shove motion has been nerfed in a patch with the addition of fatigue: do it too many times and there starts being a delay before you can do it again. This punishes the fact that you can get completely surrounded and need to shove your way out.
The reason for the nerf was that Players used to pick a corner or doorway, have a couple teammates in front who would spam the shove, and two behind them that would open fire. If a Smoker tried to pull a Survivor out of the formation, the Survivor would be quickly shoved, keeping them from getting too far. A Hunter would have no way of attacking without quickly getting shoved and shot. A Boomer would have the best chance of causing some damage, but if the Survivors picked the right spot, the Boomer wouldn't be able to get close. This type of tactic motivated Valve to both nerf the shove and create Special Infected that would break up highly coordinated Survivors in the sequel, namely, the Spitter and the Charger.
No FEMA Response: CEDA tries to respond to the "Green Flu", but gets overwhelmed. Inevitably, every time the Survivors try to get to a CEDA evacuation point, it'll be destroyed with nothing but corpses to show for it, and they'll end up having to escape another way.
Nothing Is Scarier: Hearing a sobbing Witch, knowing she's close and you have to be careful, or you'll startle her. She'll screech and try to rip you apart - and sometimes you just don't find her...
Forget Witches, sometimes you hear a special infected or its musical cue long before you see it or you know it's around the corner but don't want to be the guinea pig. The worse still, is when the Tank music starts playing but takes its time finding you so players are left frantically trying to spot it whilst trying to stick together or rethink their plans.
Notice This: Witches inexplicably cast a red light in darker areas where you would otherwise have a hard time noticing them.
Pretty Little Headshots: Headshots on witches remain effective but lack the gruesome aftermath, even if you One-Hit Kill her with a shotgun. Same goes for every Special Infected, and Commons if you're using the pistols or the Uzi.
Sound-Coded for Your Convenience: Major gameplay-changing events(horde attacks and tanks or witches being startled) change the music. Special infected spawning are accompanied by their unique theme (except in Versus) and their vocalizations give them away.
Speed Run: How some players play Versus mode as survivors. Whether this is good or bad obviously depends on opinions and situations.
Standard FPS Guns: Pistols, shotguns, assault rifles, mounted machine guns, sniper rifles, and some improvised "grenades."
Tanks can cause this singlehandedly, especially if the Survivors are clumped together and he swats a car at them. Also can happen when a good ambush is pulled off in Versus.
Averted with the Witch, who is programmed specifically to only be aggressive towards one Survivor. She was originally intended to be a threat to all survivors, running after every one of them and incapping all, but the developers figured out she was too hard to deal with like this. Not that things don't go off the rails every now and then...
Video Game Caring Potential: Given that you're trying to survive as a team in a zombie apocalypse, you can either always have your team's back, even making sacrifices to save all of their lives...
Video Game Cruelty Potential: ...or you can completely ditch them and leave them at the mercy of all the ruthless zombies, taking all the weapons and health for yourself.
Video Game Cruelty Punishment: Of course, the Director gets pissed at uncooperative play, so he'll often spawn less items and more zombies to target the cruelty-inflicting players.
Videogame Setpiece: Most prominently in the last stage of Dead Air, when the survivors leave the saferoom to see a plane on approach go out of control, impact the ground, and slide in on fire before exploding.
Violation of Common Sense: Downing a whole pack of pain pills at once would be fatal in real life, but somehow is a good idea if you're low on health.
In the zombie apocalypse, you don't need to remove the cap to swallow a whole bottle of pills.
If you get mobbed by common infected, setting yourself on fire with molotovs or blowing yourself up with a grenade launcher will usually clear your space a lot faster than to keep shoving them away or trying to hack at them all with melee weapons. You'll suffer self inflicted friendly fire damage, but that will be small compared to trying to clear out zombies invading your space without said methods.
There are some cases where team killing is actually justified. If someone is about to die and there's nothing to heal with, players will usually kill the wounded survivor and then let them respawn in a closet or revive them with a defibrillator: both methods bring the Survivor back with 50 points of health. If no one speaks of this and do the deed, they could be mistaken for a Griefer.
We Cannot Go On Without You: If there are any bots on the team, you'll have to start the level over again if all the human players are dead, regardless of if there is a bot player alive. It becomes mind-boggling when playing against a team of bot Survivors in versus mode and they are capable of moving through the level on their own without the guidance of a human player.
It gets even better when you jump off the roof of No Mercy before starting the finale with only bot allies. Game over starts playing, bots start the finale, you respawn in the closet due to finale starting, bots free you, then the game restarts the chapter anyway.
What the Hell, Player?: Shoot one of your fellow survivors, and they'll call you out for it with scripted response.
You Have Outlived Your Usefulness: Special Infected which are stuck or otherwise unable to catch up to the Survivors will occasionally be killed off by the Director, with the death noise often being faintly audible to human players, particularly in the case of Boomers and Smokers.
Tanks will fall victim to this unless they can attack the players within a given amount of time. It's rare but it does happen occasionally.
Infected players can manually trigger this when they are at a certain distance behind the survivors, allowing them to skip the respawn time that would happen if they jumped off a cliff instead.
You ALL Look Familiar: The basic infected actually have a small number of basic models but are made to look different with various filters, like clothing and blood spatter. The Unique infected all look exactly the same since they wear uniforms, aside from the CEDA zombies with different colored suits.
Zerg Rush: The AI director will send these at you when a boomer vomits on you, in pre-programmed Crescendo Events where you're forced to make a ton of noise to continue moving, or if you accidently set off a car alarm, or whenever he's bored, which isall the time. The normal infected also like to rush pipe bombs because of the smoke detector alarms rigged to them.
A.K.A.-47: Done subtly: although most of the guns are not named, zooming in on the gun models reveal they are made by fictional companies (example, the pistols in this game are made by "Finleyville Armory").
Awesome but Impractical: The minigun, which can shred oncoming hordes like no other, is never positioned so it can effectively cover more than two of the generally five or so directions that zombies can come from.
Bottomless Magazines: Pistols have infinite ammunition. This is for gameplay reasons; they don't do as much damage as regular guns, and they're the only weapons you can use while incapacitated. The creators also didn't want to ever leave you TOTALLY defenseless if you run out of ammo, either.
Gatling Good: You get the odd mounted minigun here and there. It's set up so that the gunner will have to be covered by the other Survivors, though.
Guns Akimbo: All characters can find and dual wield a second pistol for extra ammunition in the magazines.
One Bullet Clips: Applies to every weapon. Around release, however, there was a common misconception that this was averted by mag-fed weapons (read: everything but the shotguns) losing any ammo left in the current magazine when they were reloaded.note The gist of it is that, when you begin reloading a magazine-fed weapon, the ammo count in that mag is immediately dropped to zero, so then once a player starts reloading they have to take the time to let the animation play out before they can start shooting again. What players initially failed to notice is that the remaining ammo was re-added to their reserves.
Pink Mist: Pipe bombs produce this effect in the original game, rather than gibs. This was due to the performance issues of having 20 or so commons turn to gibs at once. In the sequel, pipe bombs now turn infected into gibs.
Sticks to the Back: Every primary weapon, melee weapon and medkit slot item, but not pistols (they get holsters), pill slot items, and grenades. If you examine the models in the sequel, some characters have a small rope belt that the smaller items are attached to.