I know we've done this before, but I'm too lazy to track down the thread. Still, this is too good not to share:

“I do not know how the Third World War will be fought, but I can tell you what they will use in the Fourth — rocks!”
―Albert Einstein
Source/Notes:
In an interview with Alfred Werner, published in Liberal Judaism 16 (April-May 1949). Often misquoted as "I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones."

Read more at http://izquotes.com/quote/56354