Complete the following achievements to unlock Xbox Live Gamerscore points.

Achievement	How to unlock
A Week To Live ( 25 points )	Complete 7 days in any game mode without dying.
Anniversary of the dead ( 45 points )	Complete the Final Day, in either Single or Multiplayer, and finish the game.
Can't Touch This ( 20 points )	Rack up a 100x multiplier in any game mode.
Environmental Awareness ( 5 points )	Kill a zombie using an environmental hazard in any game mode.
Friends in Low Places ( 20 points )	Save 25 survivors in any game mode.
Gas Powered ( 5 points )	Complete an entire arena, getting every kill with the Chainsaw.
Gun Shop ( 5 points )	Kill at least one zombie with each weapon type in any game mode.
Hotter Than Hell ( 25 points )	Complete the final day of the "7 Days of Hell" unlockable mode.
Interior Decorator ( 20 points )	Kill 25 zombies in any game mode using environmental hazards.
More the Merrier ( 10 points )	Kill 10 or more zombies at the same time in any game mode.
Socialite ( 5 points )	Play in an online multiplayer game.
Tour of the City ( 15 points )	Complete each arena at least once in the same game in any game mode.