Don't pull the trigger.
Make it to Safe Haven with someone named Romero in your party.
Fully upgrade your station wagon.
Kill 25 zombies without missing a shot.
Someone died of dysentery.
Successfully forde a horde of zombies 3 times.
Have $1000 on you.
Find your own grave.
Become a zombie.
Kill 500 zombies.
Put down an infected party member who has passed out.
Beat the game five times.
Beat the game on Difficult