I don't know why this is my most memorable dream because it is so short, but I had this dream when I was 5-ish and I still remember it so it must be important.
I am a little kid in New York, in the great depression, it's winter and I need a new coat. We don't have much money so my mom can't just take me to a normal store. We go through an alleyway and my mom doesn't want us to be seen by anyone so we keep having to stop because our feet are crunching in the snow and making a lot of noise. Finally we get to a little staircase/fire escape and climb up it to find the entrance to the store.
The store is really dark inside and there is only a desk and two racks of fur coats. I want to play with the coats, but my mom won't let go of my hand, she seems really worried for some reason.
The store owner arrives and my mother barters with her over the price of the coat. I look outside and see a little boy and I want to play with him so I run to the door and when I open it he is gone.
The dream ends with my mom making me wear the fur coat and leading me outside.
The dream is so odd, in that at 5 years old I had never even been to New York or learned about the great depression, I am almost convinced it must have been a book that I read and I just remember it as a dream. The really strange thing is that at 5 I was positive this was neither a dream or a book, but a memory, so one day I asked my mom if we would ever go back to the coat shop and she was really confused.
Perhaps it is one of your ancestors' memories? People on here have talked about having memories that can only come from their grandparents or some other ancestor return to them as dreams. It is fascinating stuff.
It's also interesting to think about in the context of reincarnation, if you are willing to explore belief in that sort of thing.