Successfully complete one of the following tasks to get a trophy:

  A Week to Live (Silver): Complete 7 days in any game mode without dying. 
  Anniversary of the Dead (Gold): Complete the Final Day, in either Single or 
  Multiplayer, and finish the game. 
  Can't Touch This (Bronze): Rack up a lOOx multiplier in any game mode. 
  Environmental Awareness (Bronze): Kill a zombie using an environmental hazard 
  in any game mode. 
  Friends in Low Places (Silver): Save 25 survivors in any game mode. 
  Gas Powered (Bronze): Complete an entire arena, getting every kill with the 
  Chainsaw. 
  Gun Shop (Bronze): Kill at least one zombie with each weapon type in any game 
  mode. 
  Hotter than Hell (Silver): Complete the final day of the "7 Days of Hell" 
  unlockable mode. 
  Interior Decorator (Bronze): Kill 25 zombies in any game mode using 
  environmental hazards. 
  More the Merrier (Bronze): Kill 10 or more zombies at the same time in any 
  game mode. 
  Socialite (Bronze): Play in an online multiplayer game. 
  Tour of the City (Bronze): Complete each arena at least once in the same game 
  in any game mode.