Left 4 Dead 2

Console commands
('Enable Developer Console' must be turned on in the options)
sv_cheats 1 (Turn cheats on)
*To enable cheat mode create single player game by typing "map <map name>" in console.
z_spawn (Creates a random common infected)
z_spawn  (special infected name here)
sv_infinite_ammo 1
give (item) (Gives you any item you want)
thirdpersonshoulder (Over-shoulder thirdperson view)
thirdperson - (As above, but centered view)
createhairball - (Creates a "Hairball". Usually crashes the game quite fast)
buddha 1 (Turns buddha on for ALL PLAYERS (Including bots)
god 1 - (god mode on)
noclip - (Fly through walls)
warp_far_survivor_here
nb_delete_all infected
z_common_limit 900
z_background_limit 90
z_mob_spawn_max_size 60
z_mob_spawn_min_size 50
z_no_cull 1
director_panic_forever 1
director_force_panic_event
ent_create weapon_grenade_launcher
ent_create upgrade_ammo_incendiary
ent_create upgrade_ammo_explosive
ent_create upgrade_laser_sight
prop_physics_create props_junk/explosive_box001.mdl
plugin_cvar z_specialinfectedname_health (enter number here)
Host_Timescale .4  (slow motion, can swith number for faster or slower gameplay)
Notes:
Most commands with numbers can have the number changed.
Universal Vocalize Commands
-Death Scream : Vocalize Playerdeath
-Vocalize Warn Tank : Vocalize Playeralsowarntank
-Vocalize Warn Witch : Vocalize Playeralsowarnwitch
-Vocalize Warn Boomer : Vocalize Playeralsowarnboomer
-Vocalize Warn Smoker : Vocalize Playeralsowarnsmoker
-Vocalize Using Adrenaline : Vocalize Useadrenaline
-Vocalize Hanging From Ledge: Vocalize PlayerLedgeHangEnd
-Vocalize Looking4Teammates : Vocalize Playerlostcall
-Vocalize Eating Pills : Vocalize EatPills
-Vocalize Giving Your Teammate An Item : VocalizePlayerAlertGiveItem
-Vocalize Grabbed By A Smoker : Vocalize PlayerChoke
-Ask Team If They Are Ready : Vocalize PlayerAskReady
-Ask The Team To Follow You : Vocalize PlayerFollowMe
-Vocalize Reaction To Friendly Fire : Vocalize PlayerFriendlyFire
-Ask Team To Wait For You To Heal : Vocalize PlayerHealing
-Asked Teammate To Let You Heal Them : Vocalize HealingOther
-Ask For Help : Vocalize PlayerHelp
-Vocalize Hurrah! (Encouragement) : Vocalize PLayerHurrah
-Vocalize Let's Go : Vocalize PlayerHurryUp
-Say You Agree / Are With Your Team : Vocalize PlayerImWithYou
-Let Your Team Know You're Incapped : Vocalize PLayerIncapacitated
-Notify Your Team A Horde Is Coming : Vocalize PlayerIncoming
-Tell teammate To Turn Of Their Flashlight : Vocalize PlayerKillThatLight
-Vocalize Laughing : Vocalize PlayerLaugh
-Tell A Teammate To Take The Lead : Vocalize PlayerLeadOn
-Tell You're Team You Have Fallen Off A Ledge : Vocalize PLayerLedgeHangStart
-Vocalize You're Getting Worried From Hanging : Vocalize PLayerLedgeHangMiddle
-Vocalize You're About To Fall From The Ledge : Vocalize PlayerLedgeHangEnd
-Vocalize Saving A Teammate From A Ledge : Vocalize PlayerLedgeSave
-Vocalize Saving A Teammate From A Critical Ledge Hang : Vocalize LedgeSaveCritical
-Tell Your Team/Teammate To Watch Out! : Vocalize PlayerLookOut
-Tell Your Team We Should Get Moving : Vocalize PLayerMoveOn
-Vocalize Nice Job! : Vocalize PlayerNiceJob
-Vocalize No! : Vocalize PlayerNo
-Vocalize Reviving A Teammate : Vocalize PlayerReviveFriend
-Tell your Team/Teammate You're Sorry! : Vocalize PlayerSorry
-Tell Your Team You've Found Ammo : Vocalize PlayerSpotAmmo
-Tell Your Team To Stick Together : VocalizePLayerStayTogether
-Vocalize Taunting : Vocalize playerTaunt
-Say Thank You! : Vocalize PlayerThanks
-Vocalize Being Vomitted On : Vocalize PlayerVomitInFace
-Vocalize Wait Here! : Vocalize PlayerWaithere
-Vocalize Be Careful : Vocalize PlayerWarnCareful
-Tell Your Team Infected Are Coming From Behind : Vocalize PlayerWatchOutBehind
-Vocalize Yes! : Vocalize PlayerYes
-Vocalize You're Welcome : Vocalize PLayerYouAreWelcome
-Vocalize More Casual you're Welcome : Vocalize YouWelcome
-Vocalize Look! : Vocalize SmartLook
-Vocalize Being Jockeyed : vocalize SurvivorJockeyed
-Vocalize Empathetic Run :Vocalize PlayerYellRun
''
'''How do I bind Vocalize Commands?'''
''
1. Make sure console is enabled. Esc > Options > Keyboard and Mouse > Enable Developer Console. You can then open it by pressing the tilde (~) key  at the top left of your keyboard.
2.Open console and type the following : Bind Key "Vocalize Playerdeath"
3. Now press the key you bound it to and hear the lovely sound of Vocalization.
''
'''How do I play in split-screen in the PC version?'''
''
1. Type this in console: ss_enable 1
2. Then, type in ss_map and choose a map.
3. Type in the console after its loaded connect_splitscreen localhost 2
4. After it loads you will have splitscreen.
If you want the split screen to go horizontal instead of vertical type this command in: ss_splitmode 1