Question: You are tied to a chair, and can't get up. You have a 6-shooter pistol loaded with 2 bullets pointed at your head. The 2 bullets are in adjacent chambers of the revolver. The trigger is pulled. Click. Congratulations, you're still alive. Before the trigger is pulled 1 last time, you have the option to spin the barrel, or not. Which do you choose?
Source: "How Would You move Mt Fuji" (pp 8-9, 147) by William Poundstone
Answer: This is a simple probability puzzle. If you decide to spin the barrel the odds that you'll survive another shot are 4/6 (67%) since there are 4 empty chambers out of the 6.
The 4 positions that result in empty chambers being fired, and your life being spared, are all contiguous. Furthermore, for 3 of the 4 empty chambers also have an empty chamber in the next position. Because you just had a empty chamber fire, this implies that if you decide not to spin, the chances of surviving are 3/4 = 75%. Since this is higher than 66% you definitely DON'T want to spin.