This story isn't a personal experience of mine, but it happened to my dad and he told me all about it. Now it's my turn to tell you. My dad lived in Finland when he was younger, and as you should know it gets pretty cold over there. It was a winter night and it must have been at least -2F degrees outside. My dad usually sleeps on his side and he was as asleep as anyone can get.
Well, did you ever get the feeling that someone was watching you? That's the exact feeling my dad got that night. He didn't feel like he was in danger, but feeling like you're being watched is pretty creepy. So he turned onto his back to look around his room and what he saw, he says he'll never forget. A glowing green head... Just a head, no body. It was making a really creepy face, but as I said before my dad didn't feel threatened. And just like that, the head floated out of the corner of his room. Although he wasn't in danger, he ran out of the room faster than he had ever moved, screaming. He ran outside in his underwear in -2 degree weather. His mother, my grandma, came outside and scolded him. Told him that he would catch his death of cold.
My dad tells me this is an experience he will never forget. It was the most scared he'd ever been in his life.