I believe what I will remember most from Psychology is the Fundamental Attribution Error. It is not because it was any more interesting that anything else, almost everything I learned is memorable, but I have been able to apply the Fundamental Attribution Error to many situations in my life.
On particular example is my friend who has been raised very American. Has a standard family: Mother, Father and two children, middle class, owns their own home; Very "American Dream" family just without the white picket fence. What I have realized is that my friend likes to make the fundamental attribution error by explaining things by generalizing someones personality. A situation would be during a friendly game of RISK where I was losing and to explain why, his argument was "You are just not good at strategizing". Well No. I was losing because I had the two larges empires attacking me at both sides!!! Okay, this might be a bias example.
Another example is when a friend of mine dismissed an Asian girl as stuck up and shady because she did not respond back in conversion. Not taking in the fact that the Asian girl recently immigrated her from Korea.
I was shocked that I kept finding this Error wherever I looked. And unfortunately it was more prominent in more westernized cultures. Whereas in people from eastern heritage, I was not as able to spot the fundamental attribution error.