Music.. it helps me focus, it helps me let go, it allows me to experience love, anger, hate, happiness and more all through just the power of the music and the lyrics. If I have music then I can function, without music I think I'd sink into a terrible depression and end up miserable as all hell!
Besides the obvious answer oxygen, water and food. I think I can't live without cellphone, computer and internet.
I can't live without air, food and water. The computer and internet score the last point when it comes to the question of survival...