In more mathematical settings, you can successfully condition on events with probability 0 (for instance, if (X,Y) follow a bivariate normal distribution, you might want to know the probability distribution of Y given X=x).
You can't really do this, since the answer depends on how you take the limit. You can find a limit of conditional probabilities, but saying "the probability distribution of Y given X=x" is ambiguous. This is known as the Borel-Kolmogorov paradox.
Oops. Right, I knew there were some problems here, but I thought the way I defined it I was safe. I guess not. Thanks for keeping me honest!
I was very interested in the discussions and opinions that grew out of the last time this was played, but find digging through 800+ comments for a new game to start on the same thread annoying. I also don't want this game ruined by a potential sock puppet (whom ever it may be). So here's a non-sockpuppetiered Irrationality Game, if there's still interest. If there isn't, downvote to oblivion!
The original rules:
Enjoy!