Telltale Games released the first episode of their excellent The Walking Dead game as a freebie on iOS for a limited time. In "A New Day" you meet Lee Everett who is on his way to jail when the zombie apocalypse breaks out. Lee meets Clementine, a young girl waiting for her parents, and promises to protect her.
What makes The Walking Dead a memorable game is the tough decisions you have to make. Who do you give the limited rations to? Which character do you decide to save and what kind of person is Lee?