You need help for Left 4 Dead? This is what you need:
Go in the options,mouse/keiboards,and activate console.
Then,during the game,press the tilda key,or \,1,or TAB. For my portatile is \. Oh,if they don't work,try using the shift,the press them.
now,write into the console box:
Buddha:you will receive damage,but you can't dye
give X:give any item (x=the name of the item)
God:god mode
impulse 10:ammo for all weapons
nb_blind 1:the zombie can't see you
noclip:walk trough walls
sv_infinite_ammo 1=infinite ammo for all weapons and no reloads
warp_all_survivors_here:teleport all your allies to your position
warp_to_start_area:go to the next chapter
warp_all_survivors_to_checkpoint:warp all the survivors in the nearest checkpoint
warp_all_survivors_to_finale:warp all the survivors tho the final area