I'm not sure if transformice counts as a rationalist game, but appears to be a bunch of multiplayer coordination problems, and the results seem to support ciphergoth's conjecture on intelligence levels.
Transformice is awesome :D A game hasn't made me laugh that much for a long time.
And it's about interesting, human things, like crowd behaviour and trusting the "leader" and being thrust in a position of responsibility without really knowing what to do ... oh, and everybody dying in funny ways.
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