The most popular online FPS in the world, with some claiming it generates more Internet traffic than the whole of Italy.
It's a terrorists versus counter-terrorists modification for Half Life.
It pretty much has no plot beyond "counter-terrorists must kill the terrorists and vice-versa" though there are game modes fitting the theme beyond death match such as "bomb defusal" (the only mode played in competitive matches), "rescue the hostages" (played on public servers essentially) and "escort the VIP" (never played). Various custom game modes have been introduced since: modes that limit you to specific weapons selections, modes with special, often gimmicky goals, and even maps where the object isn't to kill the opposing side but rather to navigate the map in a maze-like fashion.
Originally a free Game Mod, Valve (the developers of the original Half-Life and its sequel, Half-Life 2) has since hired on the original developers to create Counter-Strike: Source, using Half-Life 2's graphics and physics engine.
It gets a great deal of the world's top gamers. It also gets a great deal of the idiots, and also Moral Guardians who rail against it for "teaching kids to kill." Most memorable being the instance of a high school student expelled for basing a Counter-Strike map off of his school. In addition, a judge in Brazil has banned Counter-Strike sales throughout the country, because of a map designed as Rio De Janeiro. (Not that it has helped, as the game is widely pirated in Brazil).
A new version of Counter-Strike, subtitled "Global Offensive", was released in 2012.
- AKA-47 - Though there's an unofficial patch that (mostly) corrects this. Earlier versions of Counter Strike did use the real names for guns.
- Some details: There was a time (pre-Steam) where which weapon names you got depended on whether you had the mod version, which required Half Life to play (real names) or had bought the stand-alone retail version of Counter-Strike (AKA-47 names). The mod version also is the origin of the aforementioned "unofficial patch" (titles.txt).
- Depends on regions in Counter-Strike Online. Korean, Japanese and Taiwan versions straight up calls them by their original name, but Malaysian/Singapore and Indonesian versions calls it by Condition Zero titles to ease up the localization work.
- Mostly averted in Global Offensive. Most guns are called by their actual names (although without the weapon manufacturers,) with the exceptions of the sawed off Remington 870 and the Taser. The Taser uses this trope (as Taser is a brand-name,) being named the "Zeus x27," while the sawed off Remington 870 is simply called the "Sawed-Off Shotgun."
- Announcer Chatter - an extremely common server-side mod will make the game announce a "KILLING SPREE!!!", a "M-m-m-m-monster kill!!!", a "Headshot!", or a "HUMILIATION!!!" (knife kill), taken from Quake and Unreal Tournament.
- Took until Counter Strike: Source to disable this Most Annoying Sound.
- Some servers take this to a fascinating extreme, uploading dozens of sound clips to your computer when you first enter them.
- Counter-Strike Online have their own Announcer Chatter, from the standard multiple kill announcements to UT-like voice clips. Special mention goes to the nearly-haunting 10-second countdown in zombie mode.
- Armor Is Useless - You can buy a helmet, vest, or both. They barely lessen the damage taken - they're the difference between five bullets killing you and four bullets killing you. Realistically, though, the armor is more effective against sub-machine guns and pistols (except the Deagle) than against heavier arms and also protects well against grenades.
- Artistic License Geography - Condition Zero. It would be more forgivable if they didn't base some of to locale on real places in the world. Namely, Japan does not have cities sprawling with 10 foot wide roads and the only means of transportation seems to be by foot and Modesto does not look like a low-income crime ridden suburban extension from LA.
- Boom! Headshot! - FPS Doug said this while playing Counter-Strike, making it the Trope Namer.
- Cherry Tapping - Knife kills, though it has the advantage of being a one-hit kill when stabbing someone in the back.
- Counter-Strike Will Ruin Your Life: Amount of time spent playing (with some exceptions) correlates with percentage of vocabulary replaced with "AWP SUX/ROX", "N00B", "FAG", etc.
- Elaborate Underground Base - From all intents and purposes, the raid on a well-armed gang in Modesto of all places goes awry - you, a SWAT member, falls into a huge warehouse under a crime-ridden slum filled with crack for shipping and weapons.
- Escort Mission - The hostage maps, though most opt to kill the opposing team instead of saving the hostages there.
- Not to mention the CTs can claim victory on a hostage map by rescuing two hostages and then executing the other two. This is, of course, highly discouraged.
- Evil Versus Evil - The two terrorist factions fighting over the radioactive material in Deleted Scenes.
- Game Mod - In addition to the fact that this game is the most successful mod ever, custom content is very popular; note that GameBanana has more Counter-Strike: Source skins than it has skins of any other game combined.
- Guns Akimbo - Dual Beretta Elites. More useful than you think they are.
- In fact, they're the second most used, right below the Desert Eagle.
- Heroic Sacrifice - In Deleted Scenes, the Spetznaz commanding officer stays behind to make sure none of the warring terrorists disable the bomb you planted to destroy the nuclear core.
- Leeroy Jenkins - Just go on the online games. No one works together, unless they're in clans.
- Leet Lingo - Actually something of a trope popularizer for this.
- Gotten to the point that it makes one's brain hurt.
- Luckily, My Shield Will Protect Me - The Counter Terrorist's buyable equipment in Condition Zero includes a solid metal riot shield that takes up your primary slot and secondary weapon in return for blocking all forms of harm in the front while it's equipped. The first multi-player game to use this, and it was absolutely hated by pros.
- One Bullet Left - Invoked. Killing an enemy with the last bullet in your mag nets you a Steam achievement.
- Qurac - de_dust and de_dust2, and the level Recoil for Deleted Scenes.
- Real Is Brown: Global Offensive's maps are a lot less colorful than their counterparts in other games.
- Right-Handed Left-Handed Guns - Completely enforced until Global Offensive, where for the very first time in the series, there are properly modeled weapons for right-handed users.
- Some weapons in Counter-Strike Online were actually mirrored correctly.
- Right-Wing Militia Fanatic - Presumably the Militia skin for the Terrorist, and the map cs_militia.
- Sawed-Off Shotgun - Comes in three flavors, Double Barrel and the Quadbarrel for Counter-Strike Online, and a sawn-off Remington 870 called as the Sawed-Off in Global Offensive.
- Shout-Out - The manga store in the Japanese Subway level of Deleted Scenes references Read or Die amongst other manga, and the after-credits to Dr. Strangelove.
- The "1337 Krew" terrorist skin is a reskin of Gordon Freeman from Half-Life (of which the game is a mod of).
- The gang leader in "The Turn of the Screw" wears a white suit, trades in drugs, speaks with a heavy Cuban accent, and is coked up in the final battle, making him hard to kill. He screams at you all the way, and you breach the room he's hiding in with explosives.
- "Recoil", being set in Northern Africa and fighting off Jihadi after being shot down in an RPG, being a member of Delta Force and picking up a standard sniper... we'll give you two seconds. TIME'S UP! Black Hawk Down.
- Standard FPS Guns
- Sticks to the Back - At least one counter-terrorist player model in the upcoming Counter-Strike Global Offensive invert this: rifles sticks to the front when unequipped. For other games the unequipped weapon just don't appear at all.
- Played straight in Source, however.
- Super Senses - Hearing, specifically. A good player can find a nice little place to hide in, hear some footsteps, and instantly blurt out to his team "3 coming long A."
- Terrorists Without a Cause - The terrorists don't really have a mission in the normal game. Their backgrounds posit them as anti-government, anti-Western fanatics.
- Averted in Condition Zero: Deleted Scenes. Some of the terrorists who are present in multi-player actually have goals and causes (not all of them are present, though).
- Throw-Away Guns - A sometimes effective strategy, both offensively (for Leeroy Jenkinses) and defensively (No time to reload because the enemy is rushing you? Throw away your gun and grab a dead guy's gun!).
- Translation Convention/Just a Stupid Accent - In Deleted Scenes, all characters speak English [except for the opposing side], however accented.
- Western Terrorists - Militia, Arctic Avengers and Phoenix Connexion, from The US, Sweden(!) and former Soviet Union respectively.
- Averted (again) in Deleted Scenes, which features Jihadi, Filipino rebels, Japanese and Russian terrorists, bank robbers, and so on.
- You Fail Economics Forever - The short-lived attempt by Valve to dynamically price the guns - basically, trying to balance the game by having popular weapons get more and more expensive.
- Zombie Apocalypse - Comes in two flavors - Infection (which came before the Halo game mode), wherein one guy gets infected and must run around and kill the others or where the humans must escape, and NOTD/Zombie Riot, where survivors fight off an army of CPU-controlled zombies. The former usually has nigh-invulnerable zombies and forces players to hole up in buildings and last as long as possible (or escape an area), and the latter is the standard "needs a headshot" kill.
- Counter-Strike Online recycles the mods above and made it to their official playlist as Zombie Mode (Infection) and Zombie Scenario Mode (NOTD/Zombie Riot).