According to dreammoods.com:

Epic dreams (or Great dreams) are so huge, so compelling, and so vivid that you cannot ignore them. The details of such dreams remain with you for years, as if your dreamt it last night. These dreams possess much beauty and contain many archetypal symbology.  When you wake up from such a dream, you feel that you have discovered something profound or amazing about yourself or about the world. It feels like a life-changing experience.

I've had a handfull of these dreams in my life, and I've never properly documented them, so I may as well do it here, huh? The funny thing is that I've always referred to these dreams as "Epic Dreams" but never realized until I did a google search that this is actually what they are commonly referred to as.
The following dream occured sometime around age 12-13.

The dream of the Mongoose, the chipmunk and Mescalito

Eyes open...
I'm a mongoose. I'm not surprised to be a mongoose. I guess I've always been a mongoose. I am surprised, however, to find myself in a cage. I am not alone in this cage. With me is a chipmunk. Not the brightest fellow, but nice enough. Also with me is a little green man with a tall forehead, pointed ears, and short spiky black hair whom we'll call Mescalito. (NOTE: a later interpreter suggested that this figure could represent Mescalito, a figure from Native American folklore who is mentioned as a "plant ally" in the works of Carlos Castaneda. I don't know if this is accurate, but "Mescalito" is much easier to type than "Little green man", so I'll use it). To start out, our motley crew is pondering the plight of our captivity. Our cage is in a modest dwelling of wooden walls with a thatched roof. It must be summer because the windows are swung open, and the door is standing open to let in fresh air. Our captor is a Cyclops. None of us is sure what his plans for us are, but we're not eager to find out. Mescalito was the de facto leader of our strange crew of mammals and gods, and he had formulated a plan for our escape. Every day at a certain time, the Cyclops would open the front of our little cage to feed us. It was decided that the next time he came to feed us, we would force the cage door back open against his strength so we could escape. I pointed out to Mescalito that this plan could never work because even our combined physical strength would do little against that of the Cyclops. "We must use our minds' strength instead, it is there that we have the clear advantage", he replied. Later that day when he opened the front of our cage to bring in our food and water, we were ready. The chipmunk and I stood on either side of Mescalito, with our hands on his shoulders. He assumed the classical "mind powers" position of intense concentration with fingers pressed to temples. We all concentrated and focused our mental energy, and forced the cage door back against the physical strength of the cyclops. My memory here is foggy, but the cyclops lost his footing and fell back against some shelving and was at least momentarily incapacitated, allowing us to make a break from the cage and out the open door to the fields beyond. Outside the cyclops' cottage were a vast expanse of low rolling hills covered in swaying green grass. (I have since seen hills very much like this going up Interstate 5 just south of the California Bay Area). We ran, the slowed to a walk, and must have covered several miles before coming to a human sized house. Here we went in through a doggie door to seek respite from our flight. We found ourselves in a finished garage, converted into a game room (not unlike the one in my house when I was growing up, where I lived at the time of this dream). There was a pool table in the center of the room, with a pool table light hanging down over it from the ceiling. Our hopes for a rest soon disappeared, however, as the room was also occupied by a Cobra, who thought any of us might make a nice lunch. Being a mongoose, I told the others to go on ahead while I held off the snake. I proceeded to do battle with the cobra, and fared quite well. I wrestled it to the ground, plucked out it's fangs one by one, then threw it up into the pool table light where it was electricuted to death. (I've since been told that this battle bears resemblance to one in the old story "Rikki Tikki Tavi" by Rudyard Kipling. It is very much possible that I had seen the cartoon version or read the story and that it did influence this aspect of the dream). Having completed my task of dealing with the snake I went to catch up with the others, going through another doggie door into the main part of the house. At this time I was transformed into my human self, and the house was my house (although it was only my house in the dream, it didn't resemble my actual house). I said hello to my mother, as if I'd been out in the woods as usual, and went to my room. At this point I woke up.

Because of this dream, I've always considered the Mongoose to be my totem animal. Mongoose totems are generally known for courage, but for my purposes I'd just consider it a lack of fear, which isn't always the same thing.