I played a game over the weekend that seemed pretty rationalist.

There were about 6 of us, and each person had to write a famous person (living, dead, or fictional) on a piece of paper and pass it to another person. That person then had to put that paper on their forehead and try to find out who they were by asking a yes or no question (e.g. "Am I a female?", "Was I alive in the past 50 years?").

I bet a game like this could be modified further to make it more rationalist.