I usually sleep in a tank and boy shorts style underwear during the summer months. It's comfortable, I'm unencumbered and the important bits are covered in case the kids wake up in the night or something. I also like to sleep in nightgowns from time to time, but they tend to just ride up to my waist and that can be pretty annoying since I toss and turn throughout the night. During the winter, I've actually gone to bed with a hoodie on over my shirt. I absolutely hate being cold! I love flannel pajamas, too.