I've come to realize just now when I was filling out my pointless survey that my happiest moments are associated with being outdoors. Happy moments:
Walking along a creek with my first crush - it was mid April, and the snow was all melted so there was a lot of water. We explored and found a waterfall, sat and talked, walked around, all in three hours. The sun was shining, but not too strongly, and there was just the slightest breeze. One of the happiest days of my life.
Walking home from high school. It's not quite a unique event, but everytime I walked home, rain or shine, I would just remember that this world is good, that nature is beautiful.
I can't remember where this moment was exactly, but I remember being somewhere very dark, and the moon was shining on water, black water. I felt content, and didn't ever want for things to change.
Niagara Falls, standing over the falls or on Table Rock, watching it, feeling the power and surity of it, seeing the colors of the mists, the lack of buildings surrounding certain parts of it. I would stay there forever if I could, after removing all the tacky casinos behind Table Rock of course.