Too Much Has Happened For Me Not To.
Let's see here
Spirit guide: Sitting alone in the living room of my mom's boyfriend's house, I had just turned the TV off because I heard something in the hallway. I thought it was his dog so I looked, leaning off the couch. His dog is a black lab, but the dog I saw was white/silver with dark blue eyes - it looked part wolf too. I had been scared earlier because of reading those "Scary Stories to Tell in the Dark" books, but when that dog/wolf looked at me and disappeared I suddenly felt calm.
Ghosts: Two that I don't remember.
1. Sitting in my sandbox when I was younger, talking to myself (well, my mom is convinced I was talking to spirits because my grandparents' backyard is haunted)
2. At a party at a relative's house, I apparently wandered away from everyone into the woods by their house. When my mom and the others found me I said I was walking with "the people" yet I was the only one who saw or heard "the people"
UFO: In the back of my mom's boyfriend's car, we were on our way somewhere and it kind of late. I was staring out the window at this one particular star. We passed a bunch of trees, through which I could see nothing. As soon as the trees were gone, so was that star! I hadn't moved my eyes or turned my head, nothing, it was just gone!
Angels: Though I'm not religious, my grandmother has told me this story too many times for it not to have happened. My grandmother and I were going somewhere late at night, she was nearly falling asleep at the wheel. Suddenly, something bright and white flew over our car, really close. My grandma woke up, but didn't think I'd noticed anything because it was really fast. I then looked at her and asked "What was that?"
I can think of logical explanations for all but the first one. But even that little bit of doubt makes the others seem plausible.