The dream with the most impact on reality in my experience happened a couple of years ago, while I was beginning to explore Wicca. In discussion with a new colleague, we had found we lived two houses apart, and we subsequently often travelled home together. After about two weeks working together, without much intimate conversation, I had the following dream:

I was viewing the scene from a distance, and from a great height, and the "Voice", a woman who was asking questions which prompted my subconscious, asked about where I could find other Pagans to learn from. My awareness zoomed in on the house of my friend, and I saw the friend and her sister in the front garden together. The "Voice" spoke again, and said conversationally, "there used to be a brother, too; I wonder what happened to him?" The dream changed, and I woke up without any other exciting revelations.

Following that, I was most intrigued, thinking of this girl and her spiritual beliefs, and her brother; and I moved a conversation around to my own developing credence. She hedged a little, and finally I asked her outright whether she was Pagan. She hesitated then said she was a Wiccan. My jaw dropped, and I blessed my subconscious. We spoke a while longer, exploring the theme of witchcraft, and finally, near the end of the journey, I asked her, requesting she didn't laugh at me, whether she had a brother. I wasn't prepared for her reaction - she paled, and asked me why, so I explained the dream. She told me she'd had a brother, who'd died about five years ago.

Some things can be trivialised as coincidence, but I ask how trivial coincidence is.