2. I Am Legend (2007)
Being the last living man in New York is just as difficult as it sounds, especially when you're surrounded by flesh-eating former humans, and you're the last prime rib walking the streets. Luckily for Robert (Will Smith) he's kept company by Sam, a German Shepherd and the only living thing in Manhattan that does not want to eat him alive.
But during an altercation with the infected cannibals, Sam contracts the virus and Robert is forced to kill his only friend (unless you count the mannequins he sometimes chats up at the video store). We were beyond heartbroken.