Left 4 Dead

Invincibility while reloading:
Press B to reload, then hold LT to knock back attacking
zombies while reloading your gun.

Fast melee:
When using melee (LT), press Y, LT repeatedly. You will switch weapons and
melee. This helps to complete the game on the Expert difficulty from hordes of
attacking zombies.

Easy "Cr0wnd" achievement:
Play on the Easy difficulty. Get a shotgun, and find a Witch. Quickly approach
the Witch with your flashlight off. As she rises, quickly shoot her in the head
to kill her and get the "Cr0wnd" achievement.

Easy "Helping Hand" achievement:
While in a safe house, preferably one with a combat shotgun, incapacitate the
other three members of your group, then revive them. Doing this counts toward
your achievement. It is easier with a combat shotgun because it deals a lot of
damage fast. In a single player campaign, make sure all other survivors are in
the lower red health area. When you incapacitate one of them, the others will
try to revive them. You then need to shoot the others before they revive the
incapacitated players or you will not get the points for reviving.

Easy "Unbreakable" achievement:
If you have a health pack and are low on health, pause the game, and select
"Take A Break". While you are idle, you will be healed. Once you are healed,
rejoin the game, and the healing will not count against you. Note: This was
done on the Easy difficulty.


Cheat:
Be a hunter,witch,tank,smoker,boomer to be a tank,witch,hunter,boomer,smoker
press x,y,b,a.

 