Left 4 Dead 2 Cheats

Developer Console Cheats
At the main menu, select "Options", then "Keyboard/Mouse". Enable "Allow Developers Console". During gameplay, press "~" to access the console, then input the cheat.

tongue_range <#>: (Default 750) Sets the maximum range of the smoker's tongue attack
z_pounce_damage X: amount of damage you want to do to survivors
z_witch_burn_time: Amount of time before a burning Witch dies from fire (does not effect caused by fire)
z_health: Change zombie health
z_speed: Change Zombie speed
director_no_human_zombies 0/1: Disables/enables controllable Boss Infected on any map
director_panic_forever 0/1: Enables/Disables never ending panics
director_force_panic: Forces a panic event
give ammo: Full Ammunition
give pistol: Get pistol
impulse 101: Give Ammo to your primary weapon
give autoshotgun: Give auto shotgun
give first_aid_kit: give first aid kit
give health: give full health
give gascan: give gascan
give hunting_rifle: give hunting rifle
give molotov: give molotov
give oxygentank: give oxygentank
give_pain_pills: give pain pills
give pipe_bomb: give pipe bomb
give propanetank: give propanetank
give rifle: give you an MK 47 ( machine gun )
z_spawn weapon_SMG: give you the SMG
god: invincibility
buddha 1: just like god but you receive damage (sometimes if you are the only survivor left, you can't receive damage from infected

Steam Achievements
Complete each requirement to receive the achievements.
A RIDE DENIED: Kill a Jockey within 2 seconds of it jumping on a Survivor.
A SPITTLE HELP FROM MY FRIENDS: As the Spitter, spit on a Survivor being choked by a Smoker.
ACID REFLEX: Kill a Spitter before she is able to spit.
ARMORY OF ONE: Deploy an ammo upgrade and have your team use it.
BACK IN THE SADDLE: As the Jockey, ride the Survivors twice in a single life.
BARREL ROLLED: Kill a Special Infected with an exploding barrel.
BEAT THE RUSH: In a Survival match, get a medal only using melee weapons.
BRIDGE BURNER: Survive the Parish campaign.
BRIDGE OVER TREBLED SLAUGHTER: Cross the bridge finale in less than 3 minutes.
BURNING SENSATION: Ignite 50 Common Infected with incendiary ammo.
CACHE AND CARRY: Collect 15 gas cans in a single Scavenge match.
CHAIN OF COMMAND: Kill 100 Common Infected with the chainsaw.
CHAOS GENERATOR: Have all 3 generators running at once in "The Sacrifice" finale.
CL0WND: Honk the noses of 10 Clowns.
CLUB DEAD: Use every melee weapon to kill Common Infected.
CONFEDERACY OF CRUNCHES: Finish a campaign using only melee weapons.
CRASS MENAGERIE: Kill one of each Uncommon Infected.
DEAD IN THE WATER: Kill 10 swampy Mudmen while they are in the water.
DISMEMBERMENT PLAN: Kill 15 Infected with a single grenade launcher blast.
FRIED PIPER: Use a Molotov to burn a Clown leading at least 10 Common Infected.
FUEL CRISIS: Make a Survivor drop a gas can during overtime.
GAS GUZZLER: Collect 100 gas cans in Scavenge.
GAS SHORTAGE: Cause 25 gas can drops as a Special Infected.
GONG SHOW: Prove you are stronger than Moustachio.
GREAT EXPECTORATIONS: As the Spitter, hit every Survivor with a single acid patch.
GUARDIN' GNOME: Rescue Gnome Chompski from the Carnival.
HEAD HONCHO: Decapitate 200 Infected with a melee weapon.
HEARTWARMER: In a Versus match, leave the saferoom to defibrillate a dead teammate.
HUNTING PARTY: Win a game of Scavenge.
KILL BILL: Have Bill sacrifice himself for the team.
LEVEL A CHARGE: Kill a Charger with a melee weapon while they are charging someone.
LONG DISTANCE CARRIER: As the Charger, grab a Survivor and carry them over 80 feet.
MEAT TENDERIZER: As the Charger, grab a Survivor and smash them into the ground for a solid 15 seconds.
MIDNIGHT RIDER: Survive the Dark Carnival campaign.
PRICE CHOPPER: Survive the Dead Center campaign.
QUALIFIED RIDE: As the Jockey, ride a Survivor for more than 8 seconds.
RAGIN' CAJUN: Survive the Swamp Fever campaign.
ROBBED ZOMBIE: Collect 10 vials of Boomer vomit from infected CEDA agents you have killed.
RODE HARD, PUT AWAY WET: As the Jockey, ride a Survivor and steer them into a Spitter's acid patch.
SACRIFIZZLE: As a Special Infected, incap someone who is trying to sacrifice themselves.
SCATTERING RAM: As the Charger, bowl through the entire enemy team in a single charge.
SCAVENGER HUNT: Stop the enemy team from collecting any gas cans during a Scavenge match.
SEPTIC TANK: Use a bile grenade on a Tank.
SHOCK JOCK: Revive 10 dead Survivors with the defibrillator.
SOB STORY: Navigate the sugar mill and reach the safe room without killing any Witches.
SPIT HAPPENS: As the Spitter, hit every Survivor with a single acid patch.
STACHE WHACKER: Prove you are faster than Moustachio.
STILL SOMETHING TO PROVE: Survive all campaigns on Expert.
Stream Crosser: Survive the Cold Stream campaign on any difficulty.
STRENGTH IN NUMBERS: Form a team and beat an enemy team in 4v4 Versus or Scavenge.
TANK BURGER: Kill a Tank with melee weapons.
THE QUICK AND THE DEAD: Revive 10 incapacitated Survivors while under the speed boosting effects of adrenaline.
THE REAL DEAL: Survive a campaign on Expert difficulty with Realism mode enabled.
VIOLENCE IN SILENCE: Navigate the impound lot and reach the cemetary safe room without tripping any alarms.
WEATHERMAN: Survive the Hard Rain campaign.
WING AND A PRAYER: Defend yourself at the crashed airliner without taking damage.