We have covered an extensive amount of topics this semester: some more interesting than others. Personally, I found the four lectures and chapter on personality to be the most interesting and the most relevant five years from now.
This is going to sound really obvious, but everybody you will ever meet will have a different personality than the next person. Surprisingly, you don't have to spend a large amount of time with someone to figure out their general personality. By being able to read people and knowing a small amount about personality traits (i.e. Big Five), you can figure out a person's typical ways of thinking, feeling, and behaving in a relatively short amount of time. This means you will likely be able to tell whether you will like, hate, annoy, be annoyed by, laugh at, laugh with, trust, or distrust a particular person. There are other examples, but you get the general idea.
Life plans change and none of us really know where we will be or who we will be with after college. When meeting new people later on in life, knowing a little bit about personality can go a long way in your relationship (or lack thereof) with those people. It will come in very useful when you are around a new group of people: just smile, be polite, silently judge their worth to you as you pick out which ones will be your friends and enemies, or side-kicks and nemeses if you happen to be a superhero.
A little knowledge about personality can go a long way when forming new relationships with new people throughout your lifetime.