Followup to: The Most Important Thing You Learned
What's the most frequently useful thing you've learned on OB - not the most memorable or most valuable, but the thing you use most often? What influences your behavior, factors in more than one decision? Please give a concrete example if you can. This isn't limited to archetypally "mundane" activities: if your daily life involves difficult research or arguing with philosophers, go ahead and describe that too.
I tend to agree with MBlume - the most frequently used principles are probably assimilated too well. But let's see... the Bayesian worldview in general made me much more interested in probability, making me take the most "mathy" probability course in Uni early on and to plan on reading Jaynes and Pearl within the next half a year. Maybe it was The Dilemma: Science or Bayes that clinched the deal?
Skimming the list - Mind Projection Fallacy, Nobody Knows What Science Doesn't Know and Science as Attire often come to mind in contexts of what other people do wrong (I quoted the first and second principles in a few discussions). Making Beliefs Pay Rent, Mysterious Answers to Mysterious Questions, Making History Available, Cached Thoughts, Bind Yourself to Reality - I try to apply to myself on a regular basis. In my professional capacity, I try to apply (not very successfully at the moment) The Planning Fallacy and Hold Off Postponing Solutions.
The Robber's Cave Experiment was the post that got me hooked on OB in the first place. I have cited it many times. Finally, the posts on morality are frequently used in the sense that I refer myself to them every time moral discussions crop up.
I also think you should include other writings. The list you gave in the previous post does not include Robin's articles (obviously), but he certainly did leave a mark as well. (To mind come his posts on medical spending and Politics is not about Policy, but undoubtedly there are many more.)
But this is already a large list. Perhaps a series is in order, with the first book being "A Gentle Introduction".