Regarding the possible multiplayer some people are asking for, I will give my opinion on that.
First and foremost, with two players playing perfectly (remembering all the bullets, and knowing the probabilities) then the outcome of the game will be 100% determined by luck, I dont see where strategy can make one person win or lose.
Second, I have an idea which could work in multiplayer (probably there are other ones). It is to have a bullet (or more than one) were neither player knows which one is it, nor if it was already used. So for example you could have 3 normal bullets, 3 fake ones, and 1 mistery one, so you dont know the exact probability and you have to guess.