So many possibilities for the letter A!
I tumbled a bunch over in my head, I might write about more of them later, but the one I kept coming back to was the Aesir. For many Norse oriented peoples, the Aesir are the primary body of deities that are worked with. In fact, one of the major Norse faiths is called Asatru which means faith or belief in the Aesir. While other classifications of deities have some following, when you talk about deities that most people will recognize as Norse, the vast majority are Aesir.
I have read a lot of explanations of the difference between the Aesir and Vanir, and the one that resonates most with me is that the Vanir are more intimately tied to nature and hearken from an earlier time in civilization, and the Aesir then are the deities that evolved later to represent the things that people now valued. I also feel that the focus of a lot of the deities has shifted from a more personal or small clan grouping to a larger community. So while you might have had Vanir associated with hunting or even fighting, you have Aesir who are tied to battle.
I have heard a lot of people express reservations about many of the Aesir because they perceive them to be harsh or bloodthirsty. Others find this to be what draws them to the Aesir. I think that it is somewhat in between. I do see a harsh side to a lot of the Aesir, but I don't think that is the whole of who they are. This works very well for me. I am perfectly happy to live peacefully and to avoid conflict, to turn inward and pursue my own thing and leave others to their own pursuits, however if you confront me, I am not going to fold, I will call on my inner steel and meet your challenge.
One thing I always found somewhat interesting and confusing about the Aesir is that there is a lot of disagreement over who is whom. There are connections made between Freyja and Frigga or between Odin and Od. Sometimes Freyja is considered to be the Queen of Asgard and wife of Odin. When I was first starting out, I viewed Freyja and Odin as being a pair, but the more I have read and experienced, the more I don't see them as a true pairing. I think a part of this is learning about Frigga, who was not one of the first deities I learned about. I do, however, feel that Freyja and Odin have a strong relationship that has involved intimacy at times and arguments at other times. I don't feel they are the main person in each other's lives.
I think it is somewhat strange how many people classify the Aesir. I have read a lot of explanations of a sort of ruling council of gods, and most times it lists 12 gods and 13 or 14 goddesses. The gods are mostly what you would expect, though no one seems to know what to do with Loki. The goddesses are never what I would expect. Most goddess listings are Frigga and her 12 handmaidens, and these sometimes include Freyja. However goddesses like Sif aren't included. In fact there are quite a lot of Norse deities that aren't talked about much at all.
A while back I made a set of prayer cords, to help me connect with the Norse deities that I felt moved to connect with. This did include some deities that I don't consider to be Aesir, but rather Vanir or other important figures (like Hel). I was absolutely surprised when I counted up the knots at the end and found myself with fifty knots on my cord. I am so used to seeing the Norse Deities listed as a scant handful.
One thing I really appreciate about the Aesir is that they are gods, and many have powers beyond those that we as humans have, and yet, they are very human in many ways. They experience feelings: jealousy, anger, love, sadness. They make mistakes. They end up in some crazy situations that they have to wiggle their way out of.